Make tests more resilient to Skia gold failures and refactor flutter_goldens...

Make tests more resilient to Skia gold failures and refactor flutter_goldens for extensive technical debt removal (#140101)

Originally landed in https://github.com/flutter/flutter/pull/139549
Originally reverted in https://github.com/flutter/flutter/pull/140085

- Remove all use of global variables.
- Always pass in all dependencies, only create them in main or in tests.
- Pass in the "print" primitive.
- Make all network traffic retry (except when run locally, when it just auto-passes).
- Enable tests to be run in random order.
- Better error messages

dev/automated_tests/flutter_test/flutter_gold_expectation.txt

-[0-9]+:[0-9]+ [+]0: Local passes non-existent baseline for new test, null expectation *
- *No expectations provided by Skia Gold for test: library.flutter.new_golden_test.1.png. This may be a new test. If this is an unexpected result, check https://flutter-gold.skia.org.
- *Validate image output found at flutter/test/library/
-[0-9]+:[0-9]+ [+]1: Local passes non-existent baseline for new test, empty expectation *
- *No expectations provided by Skia Gold for test: library.flutter.new_golden_test.2.png. This may be a new test. If this is an unexpected result, check https://flutter-gold.skia.org.
- *Validate image output found at flutter/test/library/
 [0-9]+:[0-9]+ [+]2: All tests passed! *

dev/automated_tests/flutter_test/flutter_gold_test.dart

@@ -21,6 +21,7 @@ const List<int> _kFailPngBytes = <int>[
 ];
 
 void main() {
+  final List<String> log = <String>[];
   final MemoryFileSystem fs = MemoryFileSystem();
   final Directory basedir = fs.directory('flutter/test/library/')
     ..createSync(recursive: true);
@@ -34,6 +35,7 @@ void main() {
       environment: <String, String>{'FLUTTER_ROOT': '/flutter'},
       operatingSystem: 'macos'
     ),
+    log: log.add,
   );
 
   test('Local passes non-existent baseline for new test, null expectation', () async {
@@ -44,6 +46,12 @@ void main() {
       ),
       isTrue,
     );
+    expect(log, <String>[
+      // ignore: no_adjacent_strings_in_list
+      'No expectations provided by Skia Gold for test: library.flutter.new_golden_test.1.png. '
+      'This may be a new test. If this is an unexpected result, check https://flutter-gold.skia.org.\n'
+      'Validate image output found at flutter/test/library/'
+    ]);
   });
 
   test('Local passes non-existent baseline for new test, empty expectation', () async {
@@ -54,6 +62,16 @@ void main() {
       ),
       isTrue,
     );
+    expect(log, <String>[
+      // ignore: no_adjacent_strings_in_list
+      'No expectations provided by Skia Gold for test: library.flutter.new_golden_test.1.png. '
+      'This may be a new test. If this is an unexpected result, check https://flutter-gold.skia.org.\n'
+      'Validate image output found at flutter/test/library/',
+      // ignore: no_adjacent_strings_in_list
+      'No expectations provided by Skia Gold for test: library.flutter.new_golden_test.2.png. '
+      'This may be a new test. If this is an unexpected result, check https://flutter-gold.skia.org.\n'
+      'Validate image output found at flutter/test/library/',
+    ]);
   });
 }
 

packages/flutter/pubspec.yaml

@@ -28,6 +28,7 @@ dev_dependencies:
   async: 2.11.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   boolean_selector: 2.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   clock: 1.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
+  crypto: 3.0.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   file: 7.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   leak_tracker: 9.0.18 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   leak_tracker_testing: 1.0.6 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
@@ -41,6 +42,7 @@ dev_dependencies:
   string_scanner: 1.2.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   term_glyph: 1.2.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   test_api: 0.6.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
+  typed_data: 1.3.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   vm_service: 13.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
 
-# PUBSPEC CHECKSUM: 84b7
+# PUBSPEC CHECKSUM: e519

packages/flutter/test_private/test/pubspec.yaml

@@ -38,8 +38,10 @@ dev_dependencies:
     sdk: flutter
   fake_async: 1.3.1
 
+  crypto: 3.0.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   file: 7.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   platform: 3.1.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   process: 5.0.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
+  typed_data: 1.3.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
 
-# PUBSPEC CHECKSUM: 942d
+# PUBSPEC CHECKSUM: 5a8e

packages/flutter_goldens/README

+This package is an internal implementation detail for our testing
+infrastructure. It enables the framework to use the Skia Gold
+infrastructure for tracking golden image tests.
+
+See also:
+
+ * https://skia.org/docs/dev/testing/skiagold/
+ * https://flutter-gold.skia.org/
+ * https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package:flutter

packages/flutter_goldens/dart_test.yaml

-tags:
-  # This tag tells the test framework to not shuffle the test order according to
-  # the --test-randomize-ordering-seed for the suites that have this tag.
-  no-shuffle:
-    allow_test_randomization: false

packages/flutter_goldens/lib/flutter_goldens.dart

@@ -3,23 +3,28 @@
 // found in the LICENSE file.
 
 import 'dart:async' show FutureOr;
-import 'dart:io' as io show OSError, SocketException;
+import 'dart:io' as io;
 
 import 'package:file/file.dart';
 import 'package:file/local.dart';
 import 'package:flutter/foundation.dart';
-import 'package:flutter_goldens_client/skia_client.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:platform/platform.dart';
+import 'package:process/process.dart';
 
-export 'package:flutter_goldens_client/skia_client.dart';
+import 'skia_client.dart';
+export 'skia_client.dart';
 
 // If you are here trying to figure out how to use golden files in the Flutter
 // repo itself, consider reading this wiki page:
 // https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package%3Aflutter
 
 const String _kFlutterRootKey = 'FLUTTER_ROOT';
-final RegExp _kMainBranch = RegExp(r'master|main');
+
+bool _isMainBranch(String? branch) {
+  return branch == 'main'
+      || branch == 'master';
+}
 
 /// Main method that can be used in a `flutter_test_config.dart` file to set
 /// [goldenFileComparator] to an instance of [FlutterGoldenFileComparator] that
@@ -28,18 +33,51 @@ final RegExp _kMainBranch = RegExp(r'master|main');
 ///
 /// When set, the `namePrefix` is prepended to the names of all gold images.
 Future<void> testExecutable(FutureOr<void> Function() testMain, {String? namePrefix}) async {
+  assert(goldenFileComparator is LocalFileComparator);
   const Platform platform = LocalPlatform();
-  if (FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform)) {
-    goldenFileComparator = await FlutterPostSubmitFileComparator.fromDefaultComparator(platform, namePrefix: namePrefix);
-  } else if (FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform)) {
-    goldenFileComparator = await FlutterPreSubmitFileComparator.fromDefaultComparator(platform, namePrefix: namePrefix);
-  } else if (FlutterSkippingFileComparator.isAvailableForEnvironment(platform)) {
-    goldenFileComparator = FlutterSkippingFileComparator.fromDefaultComparator(
-      'Golden file testing is not executed on Cirrus, or LUCI environments outside of flutter/flutter.',
-        namePrefix: namePrefix
+  const FileSystem fs = LocalFileSystem();
+  const ProcessManager process = LocalProcessManager();
+  final io.HttpClient httpClient = io.HttpClient();
+  if (FlutterPostSubmitFileComparator.isRecommendedForEnvironment(platform)) {
+    goldenFileComparator = await FlutterPostSubmitFileComparator.fromLocalFileComparator(
+      localFileComparator: goldenFileComparator as LocalFileComparator,
+      namePrefix: namePrefix,
+      platform: platform,
+      fs: fs,
+      process: process,
+      httpClient: httpClient,
+      log: print,
+    );
+  } else if (FlutterPreSubmitFileComparator.isRecommendedForEnvironment(platform)) {
+    goldenFileComparator = await FlutterPreSubmitFileComparator.fromLocalFileComparator(
+      localFileComparator: goldenFileComparator as LocalFileComparator,
+      namePrefix: namePrefix,
+      platform: platform,
+      fs: fs,
+      process: process,
+      httpClient: httpClient,
+      log: print,
+    );
+  } else if (FlutterSkippingFileComparator.isRecommendedForEnvironment(platform)) {
+    goldenFileComparator = FlutterSkippingFileComparator.fromLocalFileComparator(
+      localFileComparator: goldenFileComparator as LocalFileComparator,
+      namePrefix: namePrefix,
+      reason: 'Golden file testing is not executed on Cirrus, or LUCI environments outside of flutter/flutter.',
+      platform: platform,
+      fs: fs,
+      process: process,
+      httpClient: httpClient,
+      log: print,
     );
   } else {
-    goldenFileComparator = await FlutterLocalFileComparator.fromDefaultComparator(platform);
+    goldenFileComparator = await FlutterLocalFileComparator.fromLocalFileComparator(
+      localFileComparator: goldenFileComparator as LocalFileComparator,
+      platform: platform,
+      fs: fs,
+      process: process,
+      httpClient: httpClient,
+      log: print,
+    );
   }
 
   await testMain();
@@ -88,12 +126,12 @@ abstract class FlutterGoldenFileComparator extends GoldenFileComparator {
   ///
   /// The [fs] and [platform] parameters are useful in tests, where the default
   /// file system and platform can be replaced by mock instances.
-  @visibleForTesting
   FlutterGoldenFileComparator(
     this.basedir,
     this.skiaClient, {
-    this.fs = const LocalFileSystem(),
-    this.platform = const LocalPlatform(),
+    required this.fs,
+    required this.platform,
+    required this.log,
     this.namePrefix,
   });
 
@@ -113,6 +151,9 @@ abstract class FlutterGoldenFileComparator extends GoldenFileComparator {
   @visibleForTesting
   final Platform platform;
 
+  /// The logging function to use when reporting messages to the console.
+  final LogCallback log;
+
   /// The prefix that is added to all golden names.
   final String? namePrefix;
 
@@ -135,11 +176,11 @@ abstract class FlutterGoldenFileComparator extends GoldenFileComparator {
   @protected
   @visibleForTesting
   static Directory getBaseDirectory(
-    LocalFileComparator defaultComparator,
-    Platform platform, {
+    LocalFileComparator defaultComparator, {
     String? suffix,
+    required Platform platform,
+    required FileSystem fs,
   }) {
-    const FileSystem fs = LocalFileSystem();
     final Directory flutterRoot = fs.directory(platform.environment[_kFlutterRootKey]);
     Directory comparisonRoot;
 
@@ -214,34 +255,48 @@ class FlutterPostSubmitFileComparator extends FlutterGoldenFileComparator {
   FlutterPostSubmitFileComparator(
     super.basedir,
     super.skiaClient, {
-    super.fs,
-    super.platform,
+    required super.fs,
+    required super.platform,
+    required super.log,
     super.namePrefix,
   });
 
   /// Creates a new [FlutterPostSubmitFileComparator] that mirrors the relative
   /// path resolution of the default [goldenFileComparator].
-  ///
-  /// The [goldens] and [defaultComparator] parameters are visible for testing
-  /// purposes only.
-  static Future<FlutterPostSubmitFileComparator> fromDefaultComparator(
-    final Platform platform, {
-    SkiaGoldClient? goldens,
-    LocalFileComparator? defaultComparator,
+  static Future<FlutterPostSubmitFileComparator> fromLocalFileComparator({
+    required LocalFileComparator localFileComparator,
     String? namePrefix,
+    required Platform platform,
+    required FileSystem fs,
+    required ProcessManager process,
+    required io.HttpClient httpClient,
+    required LogCallback log,
   }) async {
-
-    defaultComparator ??= goldenFileComparator as LocalFileComparator;
     final Directory baseDirectory = FlutterGoldenFileComparator.getBaseDirectory(
-      defaultComparator,
-      platform,
+      localFileComparator,
       suffix: 'flutter_goldens_postsubmit.',
+      platform: platform,
+      fs: fs,
     );
     baseDirectory.createSync(recursive: true);
 
-    goldens ??= SkiaGoldClient(baseDirectory);
+    final SkiaGoldClient goldens = SkiaGoldClient(
+      baseDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: httpClient,
+      log: log,
+    );
     await goldens.auth();
-    return FlutterPostSubmitFileComparator(baseDirectory.uri, goldens, namePrefix: namePrefix);
+    return FlutterPostSubmitFileComparator(
+      baseDirectory.uri,
+      goldens,
+      fs: fs,
+      platform: platform,
+      log: log,
+      namePrefix: namePrefix,
+    );
   }
 
   @override
@@ -250,21 +305,17 @@ class FlutterPostSubmitFileComparator extends FlutterGoldenFileComparator {
     golden = _addPrefix(golden);
     await update(golden, imageBytes);
     final File goldenFile = getGoldenFile(golden);
-
-    return skiaClient.imgtestAdd(golden.path, goldenFile);
+    await skiaClient.imgtestAdd(golden.path, goldenFile); // throws if the result is false
+    return true;
   }
 
   /// Decides based on the current environment if goldens tests should be
   /// executed through Skia Gold.
-  static bool isAvailableForEnvironment(Platform platform) {
-    final bool luciPostSubmit = platform.environment.containsKey('SWARMING_TASK_ID')
-      && platform.environment.containsKey('GOLDCTL')
-      // Luci tryjob environments contain this value to inform the [FlutterPreSubmitComparator].
-      && !platform.environment.containsKey('GOLD_TRYJOB')
-      // Only run on main branch.
-      && _kMainBranch.hasMatch(platform.environment['GIT_BRANCH'] ?? '');
-
-    return luciPostSubmit;
+  static bool isRecommendedForEnvironment(Platform platform) {
+    return platform.environment.containsKey('SWARMING_TASK_ID') // Indicates LUCI environment.
+        && platform.environment.containsKey('GOLDCTL') // Needed to use Gold.
+        && !platform.environment.containsKey('GOLD_TRYJOB') // Indicates a pre-submit environment on LUCI.
+        && _isMainBranch(platform.environment['GIT_BRANCH']);
   }
 }
 
@@ -291,41 +342,49 @@ class FlutterPreSubmitFileComparator extends FlutterGoldenFileComparator {
   FlutterPreSubmitFileComparator(
     super.basedir,
     super.skiaClient, {
-    super.fs,
-    super.platform,
+    required super.fs,
+    required super.platform,
+    required super.log,
     super.namePrefix,
   });
 
   /// Creates a new [FlutterPreSubmitFileComparator] that mirrors the
   /// relative path resolution of the default [goldenFileComparator].
-  ///
-  /// The [goldens] and [defaultComparator] parameters are visible for testing
-  /// purposes only.
-  static Future<FlutterGoldenFileComparator> fromDefaultComparator(
-    final Platform platform, {
-    SkiaGoldClient? goldens,
-    LocalFileComparator? defaultComparator,
+  static Future<FlutterGoldenFileComparator> fromLocalFileComparator({
+    required LocalFileComparator localFileComparator,
     Directory? testBasedir,
     String? namePrefix,
+    required Platform platform,
+    required FileSystem fs,
+    required ProcessManager process,
+    required io.HttpClient httpClient,
+    required LogCallback log,
   }) async {
-
-    defaultComparator ??= goldenFileComparator as LocalFileComparator;
     final Directory baseDirectory = testBasedir ?? FlutterGoldenFileComparator.getBaseDirectory(
-      defaultComparator,
-      platform,
+      localFileComparator,
       suffix: 'flutter_goldens_presubmit.',
+      platform: platform,
+      fs: fs,
     );
-
     if (!baseDirectory.existsSync()) {
       baseDirectory.createSync(recursive: true);
     }
 
-    goldens ??= SkiaGoldClient(baseDirectory);
-
+    final SkiaGoldClient goldens = SkiaGoldClient(
+      baseDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: httpClient,
+      log: log,
+    );
     await goldens.auth();
     return FlutterPreSubmitFileComparator(
       baseDirectory.uri,
-      goldens, platform: platform,
+      goldens,
+      fs: fs,
+      platform: platform,
+      log: log,
       namePrefix: namePrefix,
     );
   }
@@ -346,21 +405,19 @@ class FlutterPreSubmitFileComparator extends FlutterGoldenFileComparator {
 
   /// Decides based on the current environment if goldens tests should be
   /// executed as pre-submit tests with Skia Gold.
-  static bool isAvailableForEnvironment(Platform platform) {
-    final bool luciPreSubmit = platform.environment.containsKey('SWARMING_TASK_ID')
-      && platform.environment.containsKey('GOLDCTL')
-      && platform.environment.containsKey('GOLD_TRYJOB')
-      // Only run on the main branch
-      && _kMainBranch.hasMatch(platform.environment['GIT_BRANCH'] ?? '');
-    return luciPreSubmit;
+  static bool isRecommendedForEnvironment(Platform platform) {
+    return platform.environment.containsKey('SWARMING_TASK_ID') // Indicates LUCI environment.
+        && platform.environment.containsKey('GOLDCTL') // Needed to use Gold.
+        && platform.environment.containsKey('GOLD_TRYJOB') // Indicates a pre-submit environment on LUCI.
+        && _isMainBranch(platform.environment['GIT_BRANCH']);
   }
 }
 
 /// A [FlutterGoldenFileComparator] for testing conditions that do not execute
 /// golden file tests.
 ///
-/// Currently, this comparator is used on Cirrus, or in Luci environments when executing tests
-/// outside of the flutter/flutter repository.
+/// Currently, this comparator is used on Cirrus, or in Luci environments when
+/// executing tests outside of the flutter/flutter repository.
 ///
 /// See also:
 ///
@@ -379,6 +436,9 @@ class FlutterSkippingFileComparator extends FlutterGoldenFileComparator {
     super.basedir,
     super.skiaClient,
     this.reason, {
+    required super.fs,
+    required super.platform,
+    required super.log,
     super.namePrefix,
   });
 
@@ -387,25 +447,39 @@ class FlutterSkippingFileComparator extends FlutterGoldenFileComparator {
 
   /// Creates a new [FlutterSkippingFileComparator] that mirrors the
   /// relative path resolution of the default [goldenFileComparator].
-  static FlutterSkippingFileComparator fromDefaultComparator(
-    String reason, {
-    LocalFileComparator? defaultComparator,
+  static FlutterSkippingFileComparator fromLocalFileComparator({
+    required LocalFileComparator localFileComparator,
     String? namePrefix,
+    required String reason,
+    required FileSystem fs,
+    required ProcessManager process,
+    required Platform platform,
+    required io.HttpClient httpClient,
+    required LogCallback log,
   }) {
-    defaultComparator ??= goldenFileComparator as LocalFileComparator;
-    const FileSystem fs = LocalFileSystem();
-    final Uri basedir = defaultComparator.basedir;
-    final SkiaGoldClient skiaClient = SkiaGoldClient(fs.directory(basedir));
-    return FlutterSkippingFileComparator(basedir, skiaClient, reason, namePrefix: namePrefix);
+    final Uri basedir = localFileComparator.basedir;
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      fs.directory(basedir),
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: httpClient,
+      log: log,
+    );
+    return FlutterSkippingFileComparator(
+      basedir,
+      skiaClient,
+      reason,
+      fs: fs,
+      platform: platform,
+      log: log,
+      namePrefix: namePrefix,
+    );
   }
 
   @override
   Future<bool> compare(Uint8List imageBytes, Uri golden) async {
-    // Ideally we would use markTestSkipped here but in some situations,
-    // comparators are called outside of tests.
-    // See also: https://github.com/flutter/flutter/issues/91285
-    // ignore: avoid_print
-    print('Skipping "$golden" test: $reason');
+    log('Auto-passing "$golden" test without checking: $reason');
     return true;
   }
 
@@ -416,13 +490,10 @@ class FlutterSkippingFileComparator extends FlutterGoldenFileComparator {
   /// used.
   ///
   /// If we are in a CI environment, LUCI or Cirrus, but are not using the other
-  /// comparators, we skip.
-  static bool isAvailableForEnvironment(Platform platform) {
-    return (platform.environment.containsKey('SWARMING_TASK_ID')
-      // Some builds are still being run on Cirrus, we should skip these.
-      || platform.environment.containsKey('CIRRUS_CI'))
-      // If we are in CI, skip on branches that are not main.
-      && !_kMainBranch.hasMatch(platform.environment['GIT_BRANCH'] ?? '');
+  /// comparators (determined by checking this after the others), we skip.
+  static bool isRecommendedForEnvironment(Platform platform) {
+    return platform.environment.containsKey('SWARMING_TASK_ID') // Indicates LUCI environment.
+        || platform.environment.containsKey('CIRRUS_CI'); // Indicates Cirrus environment.
   }
 }
 
@@ -432,7 +503,7 @@ class FlutterSkippingFileComparator extends FlutterGoldenFileComparator {
 /// This comparator utilizes the [SkiaGoldClient] to request baseline images for
 /// the given device under test for comparison. This comparator is initialized
 /// when conditions for all other [FlutterGoldenFileComparators] have not been
-/// met, see the `isAvailableForEnvironment` method for each one listed below.
+/// met, see the `isRecommendedForEnvironment` method for each one listed below.
 ///
 /// The [FlutterLocalFileComparator] is intended to run on local machines and
 /// serve as a smoke test during development. As such, it will not be able to
@@ -461,52 +532,45 @@ class FlutterLocalFileComparator extends FlutterGoldenFileComparator with LocalC
   FlutterLocalFileComparator(
     super.basedir,
     super.skiaClient, {
-    super.fs,
-    super.platform,
+    required super.fs,
+    required super.platform,
+    required super.log,
   });
 
   /// Creates a new [FlutterLocalFileComparator] that mirrors the
   /// relative path resolution of the default [goldenFileComparator].
-  ///
-  /// The [goldens], [defaultComparator], and [baseDirectory] parameters are
-  /// visible for testing purposes only.
-  static Future<FlutterGoldenFileComparator> fromDefaultComparator(
-    final Platform platform, {
-    SkiaGoldClient? goldens,
-    LocalFileComparator? defaultComparator,
-    Directory? baseDirectory,
+  static Future<FlutterGoldenFileComparator> fromLocalFileComparator({
+    required LocalFileComparator localFileComparator,
+    required Platform platform,
+    required FileSystem fs,
+    required ProcessManager process,
+    required io.HttpClient httpClient,
+    required LogCallback log,
   }) async {
-    defaultComparator ??= goldenFileComparator as LocalFileComparator;
-    baseDirectory ??= FlutterGoldenFileComparator.getBaseDirectory(
-      defaultComparator,
-      platform,
+    final Directory baseDirectory = FlutterGoldenFileComparator.getBaseDirectory(
+      localFileComparator,
+      platform: platform,
+      fs: fs,
     );
-
     if (!baseDirectory.existsSync()) {
       baseDirectory.createSync(recursive: true);
     }
 
-    goldens ??= SkiaGoldClient(baseDirectory);
-    try {
-      // Check if we can reach Gold.
-      await goldens.getExpectationForTest('');
-    } on io.OSError catch (_) {
-      return FlutterSkippingFileComparator(
-        baseDirectory.uri,
-        goldens,
-        'OSError occurred, could not reach Gold. '
-          'Switching to FlutterSkippingGoldenFileComparator.',
-      );
-    } on io.SocketException catch (_) {
-      return FlutterSkippingFileComparator(
-        baseDirectory.uri,
-        goldens,
-        'SocketException occurred, could not reach Gold. '
-          'Switching to FlutterSkippingGoldenFileComparator.',
-      );
-    }
-
-    return FlutterLocalFileComparator(baseDirectory.uri, goldens);
+    final SkiaGoldClient goldens = SkiaGoldClient(
+      baseDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: httpClient,
+      log: log,
+    );
+    return FlutterLocalFileComparator(
+      baseDirectory.uri,
+      goldens,
+      fs: fs,
+      platform: platform,
+      log: log,
+    );
   }
 
   @override
@@ -514,21 +578,24 @@ class FlutterLocalFileComparator extends FlutterGoldenFileComparator with LocalC
     golden = _addPrefix(golden);
     final String testName = skiaClient.cleanTestName(golden.path);
     late String? testExpectation;
-    testExpectation = await skiaClient.getExpectationForTest(testName);
-
-    if (testExpectation == null || testExpectation.isEmpty) {
-      // There is no baseline for this test.
-      // Ideally we would use markTestSkipped here but in some situations,
-      // comparators are called outside of tests.
-      // See also: https://github.com/flutter/flutter/issues/91285
-      // ignore: avoid_print
-      print(
-        'No expectations provided by Skia Gold for test: $golden. '
-        'This may be a new test. If this is an unexpected result, check '
-        'https://flutter-gold.skia.org.\n'
-        'Validate image output found at $basedir'
-      );
-      update(golden, imageBytes);
+    try {
+      testExpectation = await skiaClient.getExpectationForTest(testName);
+      if (testExpectation == null || testExpectation.isEmpty) {
+        log(
+          'No expectations provided by Skia Gold for test: $golden. '
+          'This may be a new test. If this is an unexpected result, check '
+          'https://flutter-gold.skia.org.\n'
+          'Validate image output found at $basedir'
+        );
+        update(golden, imageBytes);
+        return true;
+      }
+    } on Exception catch (error) {
+      if (error is! io.SocketException &&
+          error is! io.OSError) {
+        rethrow; // "uncaught error"
+      }
+      log('Auto-passing "$golden" test, ignoring network error when contacting Skia.');
       return true;
     }
 

packages/flutter_goldens_client/lib/skia_client.dart → packages/flutter_goldens/lib/skia_client.dart

@@ -7,7 +7,6 @@ import 'dart:io' as io;
 
 import 'package:crypto/crypto.dart';
 import 'package:file/file.dart';
-import 'package:file/local.dart';
 import 'package:path/path.dart' as path;
 import 'package:platform/platform.dart';
 import 'package:process/process.dart';
@@ -21,6 +20,17 @@ const String _kGoldctlKey = 'GOLDCTL';
 const String _kTestBrowserKey = 'FLUTTER_TEST_BROWSER';
 const String _kWebRendererKey = 'FLUTTER_WEB_RENDERER';
 
+/// Signature of callbacks used to inject [print] replacements.
+typedef LogCallback = void Function(String);
+
+/// Signature of callbacks used to determine if a Skia Gold command succeeded,
+/// and if not, what the error message should be.
+///
+/// Return null if the given arguments indicate success.
+///
+/// Otherwise, return the error message to show.
+typedef SkiaErrorCallback = String? Function(int exitCode, String stdout, String stderr);
+
 /// Exception thrown when an error is returned from the [SkiaClient].
 class SkiaException implements Exception {
   /// Creates a new `SkiaException` with a required error [message].
@@ -40,16 +50,14 @@ class SkiaException implements Exception {
 /// Flutter Gold Dashboard.
 class SkiaGoldClient {
   /// Creates a [SkiaGoldClient] with the given [workDirectory].
-  ///
-  /// All other parameters are optional. They may be provided in tests to
-  /// override the defaults for [fs], [process], [platform], and [httpClient].
   SkiaGoldClient(
     this.workDirectory, {
-    this.fs = const LocalFileSystem(),
-    this.process = const LocalProcessManager(),
-    this.platform = const LocalPlatform(),
-    io.HttpClient? httpClient,
-  }) : httpClient = httpClient ?? io.HttpClient();
+    required this.fs,
+    required this.process,
+    required this.platform,
+    required this.httpClient,
+    required this.log,
+  });
 
   /// The file system to use for storing the local clone of the repository.
   ///
@@ -57,12 +65,6 @@ class SkiaGoldClient {
   /// replaced by a memory file system.
   final FileSystem fs;
 
-  /// A wrapper for the [dart:io.Platform] API.
-  ///
-  /// This is useful in tests, where the system platform (the default) can be
-  /// replaced by a mock platform instance.
-  final Platform platform;
-
   /// A controller for launching sub-processes.
   ///
   /// This is useful in tests, where the real process manager (the default) can
@@ -70,9 +72,18 @@ class SkiaGoldClient {
   /// sub-processes.
   final ProcessManager process;
 
+  /// A wrapper for the [dart:io.Platform] API.
+  ///
+  /// This is useful in tests, where the system platform (the default) can be
+  /// replaced by a mock platform instance.
+  final Platform platform;
+
   /// A client for making Http requests to the Flutter Gold dashboard.
   final io.HttpClient httpClient;
 
+  /// The logging function to use when reporting messages to the console.
+  final void Function(String message) log;
+
   /// The local [Directory] within the [comparisonRoot] for the current test
   /// context. In this directory, the client will create image and JSON files
   /// for the goldctl tool to use.
@@ -91,38 +102,117 @@ class SkiaGoldClient {
   /// Uses the [platform] environment in this implementation.
   String get _goldctl => platform.environment[_kGoldctlKey]!;
 
+  static void _indent(LogCallback writeln, String text) {
+    if (text.isEmpty) {
+      writeln('  <empty>');
+    } else {
+      for (final String line in text.split('\n')) {
+        writeln('  $line');
+      }
+    }
+  }
+
+  static void _dump(LogCallback writeln, String data, String label) {
+    if (data.isNotEmpty) {
+      writeln('');
+      writeln('$label:');
+      _indent(writeln, data);
+    }
+  }
+
+  Future<void> _retry({
+    required Future<io.ProcessResult> Function() task,
+    required String taskName,
+    SkiaErrorCallback? errorMessage,
+  }) async {
+    Duration delay = const Duration(seconds: 5);
+    while (true) {
+      final io.ProcessResult result = await task();
+      final String resultStdout = result.stdout as String;
+      final String resultStderr = result.stderr as String;
+
+      if (result.exitCode != 0 && resultStdout.contains('resulted in a 502: 502 Bad Gateway')) {
+        // Probably a transient error, try again.
+        // (See https://issues.skia.org/issues/40044713)
+        //
+        // This could have false-positives, because there's no standard format
+        // for the error messages from Skia gold. Maybe the test name is output
+        // and the test name contains the string above, who knows. For now it
+        // seems more likely that the server is flaking than that there's a
+        // false positive, and false positives seem less likely to be flaky so
+        // we're likely to catch them when they happen.
+        log('Transient failure (exit code ${result.exitCode}) from Skia Gold.');
+        _dump(log, resultStdout, 'stdout from gold');
+        _dump(log, resultStderr, 'stderr from gold');
+        log('');
+        log('Retrying in ${delay.inSeconds} seconds.');
+        await Future<void>.delayed(delay);
+        delay *= 2;
+        continue; // retry
+      }
+
+      String? message;
+      if (errorMessage != null) {
+        message = errorMessage(result.exitCode, resultStdout, resultStderr);
+        if (message == null) {
+          return; // success
+        }
+      } else {
+        if (result.exitCode == 0) {
+          return; // success
+        }
+      }
+
+      final StringBuffer buffer = StringBuffer();
+      if (message != null) {
+        buffer.writeln(message);
+        buffer.writeln();
+      }
+      buffer.writeln('$taskName failed with exit code ${result.exitCode}.');
+      _dump(buffer.writeln, resultStdout, 'stdout from gold');
+      _dump(buffer.writeln, resultStderr, 'stderr from gold');
+      final File resultFile = workDirectory.childFile('result-state.json');
+      if (await resultFile.exists()) {
+        _dump(buffer.writeln, resultFile.readAsStringSync(), 'result-state.json contents');
+      }
+      throw SkiaException(buffer.toString()); // failure
+    }
+  }
+
   /// Prepares the local work space for golden file testing and calls the
   /// goldctl `auth` command.
   ///
   /// This ensures that the goldctl tool is authorized and ready for testing.
   /// Used by the [FlutterPostSubmitFileComparator] and the
   /// [FlutterPreSubmitFileComparator].
+  ///
+  /// Does nothing if [clientIsAuthorized] returns true.
   Future<void> auth() async {
     if (await clientIsAuthorized()) {
       return;
     }
-    final List<String> authCommand = <String>[
-      _goldctl,
-      'auth',
-      '--work-dir', workDirectory
-        .childDirectory('temp')
-        .path,
-      '--luci',
-    ];
 
-    final io.ProcessResult result = await process.run(authCommand);
-
-    if (result.exitCode != 0) {
-      final StringBuffer buf = StringBuffer()
-        ..writeln('Skia Gold authorization failed.')
-        ..writeln('Luci environments authenticate using the file provided '
-          'by LUCI_CONTEXT. There may be an error with this file or Gold '
-          'authentication.')
-        ..writeln('Debug information for Gold --------------------------------')
-        ..writeln('stdout: ${result.stdout}')
-        ..writeln('stderr: ${result.stderr}');
-      throw SkiaException(buf.toString());
-    }
+    await _retry(
+      task: () => process.run(<String>[
+        _goldctl,
+        'auth',
+        '--work-dir', workDirectory
+          .childDirectory('temp')
+          .path,
+        '--luci',
+      ]),
+      taskName: 'auth',
+      errorMessage: (int exitCode, String resultStdout, String resultStderr) {
+        if (exitCode == 0) {
+          return null;
+        }
+        return 'Skia Gold authorization failed.\n'
+               '\n'
+               'Luci environments authenticate using the file provided by '
+               'LUCI_CONTEXT. There may be an error with this file or Gold '
+               'authentication.';
+      },
+    );
   }
 
   /// Signals if this client is initialized for uploading images to the Gold
@@ -138,6 +228,8 @@ class SkiaGoldClient {
   /// The `imgtest` command collects and uploads test results to the Skia Gold
   /// backend, the `init` argument initializes the current test. Used by the
   /// [FlutterPostSubmitFileComparator].
+  ///
+  /// This function is idempotent.
   Future<void> imgtestInit() async {
     // This client has already been initialized
     if (_initialized) {
@@ -173,20 +265,16 @@ class SkiaGoldClient {
       throw SkiaException(buf.toString());
     }
 
-    final io.ProcessResult result = await process.run(imgtestInitCommand);
-
-    if (result.exitCode != 0) {
-      _initialized = false;
-      final StringBuffer buf = StringBuffer()
-        ..writeln('Skia Gold imgtest init failed.')
-        ..writeln('An error occurred when initializing golden file test with ')
-        ..writeln('goldctl.')
-        ..writeln()
-        ..writeln('Debug information for Gold --------------------------------')
-        ..writeln('stdout: ${result.stdout}')
-        ..writeln('stderr: ${result.stderr}');
-      throw SkiaException(buf.toString());
-    }
+    await _retry(
+      task: () => process.run(imgtestInitCommand),
+      taskName: 'imgtest init',
+      errorMessage: (int exitCode, String resultStdout, String resultStderr) {
+        if (exitCode == 0) {
+          return null;
+        }
+        return 'An error occurred when initializing golden file test with goldctl.';
+      },
+    );
     _initialized = true;
   }
 
@@ -197,53 +285,43 @@ class SkiaGoldClient {
   /// returned from the invocation of this command that indicates a pass or fail
   /// result.
   ///
+  /// If an unapproved image has made it to post-submit, this throws, to close
+  /// the tree.
+  ///
   /// The [testName] and [goldenFile] parameters reference the current
   /// comparison being evaluated by the [FlutterPostSubmitFileComparator].
-  Future<bool> imgtestAdd(String testName, File goldenFile) async {
-    final List<String> imgtestCommand = <String>[
-      _goldctl,
-      'imgtest', 'add',
-      '--work-dir', workDirectory
-        .childDirectory('temp')
-        .path,
-      '--test-name', cleanTestName(testName),
-      '--png-file', goldenFile.path,
-      '--passfail',
-      ..._getPixelMatchingArguments(),
-    ];
-
-    final io.ProcessResult result = await process.run(imgtestCommand);
-
-    if (result.exitCode != 0) {
-      // If an unapproved image has made it to post-submit, throw to close the
-      // tree.
-      String? resultContents;
-      final File resultFile = workDirectory.childFile(fs.path.join(
-        'result-state.json',
-      ));
-      if (await resultFile.exists()) {
-        resultContents = await resultFile.readAsString();
-      }
-
-      final StringBuffer buf = StringBuffer()
-        ..writeln('Skia Gold received an unapproved image in post-submit ')
-        ..writeln('testing. Golden file images in flutter/flutter are triaged ')
-        ..writeln('in pre-submit during code review for the given PR.')
-        ..writeln()
-        ..writeln('Visit https://flutter-gold.skia.org/ to view and approve ')
-        ..writeln('the image(s), or revert the associated change. For more ')
-        ..writeln('information, visit the wiki: ')
-        ..writeln('https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package:flutter')
-        ..writeln()
-        ..writeln('Debug information for Gold --------------------------------')
-        ..writeln('stdout: ${result.stdout}')
-        ..writeln('stderr: ${result.stderr}')
-        ..writeln()
-        ..writeln('result-state.json: ${resultContents ?? 'No result file found.'}');
-      throw SkiaException(buf.toString());
-    }
-
-    return true;
+  Future<void> imgtestAdd(String testName, File goldenFile) async {
+    await _retry(
+      task: () => process.run(<String>[
+        _goldctl,
+        'imgtest', 'add',
+        '--work-dir', workDirectory
+          .childDirectory('temp')
+          .path,
+        '--test-name', cleanTestName(testName),
+        '--png-file', goldenFile.path,
+        '--passfail',
+        ..._getPixelMatchingArguments(),
+      ]),
+      taskName: 'imgtest add',
+      errorMessage: (int exitCode, String resultStdout, String resultStderr) {
+        if (exitCode == 0) {
+          return null;
+        }
+        if (resultStdout.contains('Untriaged') ||
+            resultStdout.contains('negative image')) {
+          return 'Skia Gold received an unapproved image in post-submit '
+                 'testing. Golden file images in flutter/flutter are triaged '
+                 'in pre-submit during code review for the given PR.\n'
+                 '\n'
+                 'Visit https://flutter-gold.skia.org/ to view and approve '
+                 'the image(s), or revert the associated change. For more '
+                 'information, visit the wiki:\n'
+                 '  https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package:flutter';
+        }
+        return 'Golden test for "$testName" failed for a reason unrelated to pixel comparison.';
+      },
+    );
   }
 
   /// Signals if this client is initialized for uploading tryjobs to the Gold
@@ -259,6 +337,8 @@ class SkiaGoldClient {
   /// The `imgtest` command collects and uploads test results to the Skia Gold
   /// backend, the `init` argument initializes the current tryjob. Used by the
   /// [FlutterPreSubmitFileComparator].
+  ///
+  /// This function is idempotent.
   Future<void> tryjobInit() async {
     // This client has already been initialized
     if (_tryjobInitialized) {
@@ -297,20 +377,16 @@ class SkiaGoldClient {
       throw SkiaException(buf.toString());
     }
 
-    final io.ProcessResult result = await process.run(imgtestInitCommand);
-
-    if (result.exitCode != 0) {
-      _tryjobInitialized = false;
-      final StringBuffer buf = StringBuffer()
-        ..writeln('Skia Gold tryjobInit failure.')
-        ..writeln('An error occurred when initializing golden file tryjob with ')
-        ..writeln('goldctl.')
-        ..writeln()
-        ..writeln('Debug information for Gold --------------------------------')
-        ..writeln('stdout: ${result.stdout}')
-        ..writeln('stderr: ${result.stderr}');
-      throw SkiaException(buf.toString());
-    }
+    await _retry(
+      task: () => process.run(imgtestInitCommand),
+      taskName: 'imgtest init',
+      errorMessage: (int exitCode, String resultStdout, String resultStderr) {
+        if (exitCode == 0) {
+          return null;
+        }
+        return 'An error occurred when initializing golden file tryjob with goldctl.';
+      },
+    );
     _tryjobInitialized = true;
   }
 
@@ -324,42 +400,25 @@ class SkiaGoldClient {
   /// The [testName] and [goldenFile] parameters reference the current
   /// comparison being evaluated by the [FlutterPreSubmitFileComparator].
   Future<void> tryjobAdd(String testName, File goldenFile) async {
-    final List<String> imgtestCommand = <String>[
-      _goldctl,
-      'imgtest', 'add',
-      '--work-dir', workDirectory
-        .childDirectory('temp')
-        .path,
-      '--test-name', cleanTestName(testName),
-      '--png-file', goldenFile.path,
-      ..._getPixelMatchingArguments(),
-    ];
-
-    final io.ProcessResult result = await process.run(imgtestCommand);
-
-    final String/*!*/ resultStdout = result.stdout.toString();
-    if (result.exitCode != 0 &&
-      !(resultStdout.contains('Untriaged') || resultStdout.contains('negative image'))) {
-      String? resultContents;
-      final File resultFile = workDirectory.childFile(fs.path.join(
-        'result-state.json',
-      ));
-      if (await resultFile.exists()) {
-        resultContents = await resultFile.readAsString();
-      }
-      final StringBuffer buf = StringBuffer()
-        ..writeln('Unexpected Gold tryjobAdd failure.')
-        ..writeln('Tryjob execution for golden file test $testName failed for')
-        ..writeln('a reason unrelated to pixel comparison.')
-        ..writeln()
-        ..writeln('Debug information for Gold --------------------------------')
-        ..writeln('stdout: ${result.stdout}')
-        ..writeln('stderr: ${result.stderr}')
-        ..writeln()
-        ..writeln()
-        ..writeln('result-state.json: ${resultContents ?? 'No result file found.'}');
-      throw SkiaException(buf.toString());
-    }
+    await _retry(
+      task: () => process.run(<String>[
+        _goldctl,
+        'imgtest', 'add',
+        '--work-dir', workDirectory.childDirectory('temp').path,
+        '--test-name', cleanTestName(testName),
+        '--png-file', goldenFile.path,
+        ..._getPixelMatchingArguments(),
+      ]),
+      taskName: 'imgtest add',
+      errorMessage: (int exitCode, String resultStdout, String resultStderr) {
+        if (exitCode == 0 ||
+            resultStdout.contains('Untriaged') ||
+            resultStdout.contains('negative image')) {
+          return null;
+        }
+        return 'Golden test for "$testName" failed for a reason unrelated to pixel comparison.';
+      },
+    );
   }
 
   // Constructs arguments for `goldctl` for controlling how pixels are compared.
@@ -408,58 +467,45 @@ class SkiaGoldClient {
   }
 
   /// Returns the latest positive digest for the given test known to Flutter
-  /// Gold at head.
+  /// Gold at head. Throws without retrying if there's a network failure.
   Future<String?> getExpectationForTest(String testName) async {
-    late String? expectation;
     final String traceID = getTraceID(testName);
-    await io.HttpOverrides.runWithHttpOverrides<Future<void>>(() async {
-      final Uri requestForExpectations = Uri.parse(
-        'https://flutter-gold.skia.org/json/v2/latestpositivedigest/$traceID'
-      );
-      late String rawResponse;
-      try {
-        final io.HttpClientRequest request = await httpClient.getUrl(requestForExpectations);
-        final io.HttpClientResponse response = await request.close();
-        rawResponse = await utf8.decodeStream(response);
-        final dynamic jsonResponse = json.decode(rawResponse);
-        if (jsonResponse is! Map<String, dynamic>) {
-          throw const FormatException('Skia gold expectations do not match expected format.');
-        }
-        expectation = jsonResponse['digest'] as String?;
-      } on FormatException catch (error) {
-        // Ideally we'd use something like package:test's printOnError, but best reliability
-        // in getting logs on CI for now we're just using print.
-        // See also: https://github.com/flutter/flutter/issues/91285
-        print( // ignore: avoid_print
-          'Formatting error detected requesting expectations from Flutter Gold.\n'
-          'error: $error\n'
-          'url: $requestForExpectations\n'
-          'response: $rawResponse'
-        );
-        rethrow;
-      }
-    },
-      SkiaGoldHttpOverrides(),
+    final Uri requestForExpectations = Uri.parse(
+      'https://flutter-gold.skia.org/json/v2/latestpositivedigest/$traceID'
     );
-    return expectation;
+    String? rawResponse;
+    try {
+      final io.HttpClientRequest request = await httpClient.getUrl(requestForExpectations);
+      final io.HttpClientResponse response = await request.close();
+      rawResponse = await utf8.decodeStream(response);
+      final dynamic jsonResponse = json.decode(rawResponse);
+      if (jsonResponse is! Map<String, dynamic>) {
+        throw const FormatException('Skia gold expectations do not match expected format.');
+      }
+      return jsonResponse['digest'] as String?; // success
+    } on FormatException catch (error) {
+      log(
+        'Formatting error detected requesting expectations from Flutter Gold.\n'
+        'error: $error\n'
+        'url: $requestForExpectations\n'
+        'response: $rawResponse'
+      );
+      rethrow; // fail
+    }
   }
 
   /// Returns a list of bytes representing the golden image retrieved from the
   /// Flutter Gold dashboard.
   ///
   /// The provided image hash represents an expectation from Flutter Gold.
-  Future<List<int>>getImageBytes(String imageHash) async {
+  Future<List<int>> getImageBytes(String imageHash) async {
     final List<int> imageBytes = <int>[];
-    await io.HttpOverrides.runWithHttpOverrides<Future<void>>(() async {
-      final Uri requestForImage = Uri.parse(
-        'https://flutter-gold.skia.org/img/images/$imageHash.png',
-      );
-      final io.HttpClientRequest request = await httpClient.getUrl(requestForImage);
-      final io.HttpClientResponse response = await request.close();
-      await response.forEach((List<int> bytes) => imageBytes.addAll(bytes));
-    },
-      SkiaGoldHttpOverrides(),
+    final Uri requestForImage = Uri.parse(
+      'https://flutter-gold.skia.org/img/images/$imageHash.png',
     );
+    final io.HttpClientRequest request = await httpClient.getUrl(requestForImage);
+    final io.HttpClientResponse response = await request.close();
+    await response.forEach((List<int> bytes) => imageBytes.addAll(bytes));
     return imageBytes;
   }
 
@@ -512,7 +558,7 @@ class SkiaGoldClient {
     final File authFile = workDirectory.childFile(fs.path.join(
       'temp',
       'auth_opt.json',
-    ))/*!*/;
+    ));
 
     if (await authFile.exists()) {
       final String contents = await authFile.readAsString();
@@ -568,6 +614,3 @@ class SkiaGoldClient {
     return md5Sum;
   }
 }
-
-/// Used to make HttpRequests during testing.
-class SkiaGoldHttpOverrides extends io.HttpOverrides { }

packages/flutter_goldens/pubspec.yaml

@@ -9,26 +9,24 @@ dependencies:
     sdk: flutter
   flutter_test:
     sdk: flutter
-  flutter_goldens_client:
-    path: ../flutter_goldens_client
   file: 7.0.0
   meta: 1.11.0
   platform: 3.1.3
   process: 5.0.1
+  crypto: 3.0.3
+  path: 1.9.0
 
   async: 2.11.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   boolean_selector: 2.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   characters: 1.3.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   clock: 1.1.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   collection: 1.18.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
-  crypto: 3.0.3 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   fake_async: 1.3.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   leak_tracker: 9.0.18 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   leak_tracker_flutter_testing: 2.0.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   leak_tracker_testing: 1.0.6 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   matcher: 0.12.16+1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   material_color_utilities: 0.8.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
-  path: 1.9.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   source_span: 1.10.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   stack_trace: 1.11.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   stream_channel: 2.1.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"

packages/flutter_goldens/test/comparator_selection_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_goldens/flutter_goldens.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:platform/platform.dart';
+
+enum _Comparator { post, pre, skip, local }
+
+_Comparator _testRecommendations({
+  bool hasFlutterRoot = false,
+  bool hasLuci = false,
+  bool hasCirrus = false,
+  bool hasGold = false,
+  bool hasTryJob = false,
+  String branch = 'main',
+  String os = 'macos',
+}) {
+  final Platform platform = FakePlatform(
+    environment: <String, String>{
+      if (hasFlutterRoot)
+        'FLUTTER_ROOT': '/flutter',
+      if (hasLuci)
+        'SWARMING_TASK_ID': '8675309',
+      if (hasCirrus)
+        'CIRRUS_CI': 'true',
+      if (hasCirrus)
+        'CIRRUS_PR': '',
+      if (hasCirrus)
+        'CIRRUS_BRANCH': branch,
+      if (hasGold)
+        'GOLDCTL': 'goldctl',
+      if (hasGold && hasCirrus)
+        'GOLD_SERVICE_ACCOUNT': 'service account...',
+      if (hasTryJob)
+        'GOLD_TRYJOB': 'git/ref/12345/head',
+      'GIT_BRANCH': branch,
+    },
+    operatingSystem: os,
+  );
+  if (FlutterPostSubmitFileComparator.isRecommendedForEnvironment(platform)) {
+    return _Comparator.post;
+  }
+  if (FlutterPreSubmitFileComparator.isRecommendedForEnvironment(platform)) {
+    return _Comparator.pre;
+  }
+  if (FlutterSkippingFileComparator.isRecommendedForEnvironment(platform)) {
+    return _Comparator.skip;
+  }
+  return _Comparator.local;
+}
+
+void main() {
+  test('Comparator recommendations - main branch', () {
+    // If we're running locally (no CI), use a local comparator.
+    expect(_testRecommendations(), _Comparator.local);
+    expect(_testRecommendations(hasFlutterRoot: true), _Comparator.local);
+    expect(_testRecommendations(hasGold: true), _Comparator.local);
+    expect(_testRecommendations(hasFlutterRoot: true, hasGold: true), _Comparator.local);
+
+    // If we don't have gold but are on CI, we skip regardless.
+    expect(_testRecommendations(hasLuci: true), _Comparator.skip);
+    expect(_testRecommendations(hasLuci: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(hasLuci: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true), _Comparator.skip);
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(hasFlutterRoot: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+
+    // On Luci, with Gold, post-submit. Flutter root and Cirrus variables should have no effect.
+    expect(_testRecommendations(hasGold: true, hasLuci: true), _Comparator.post);
+    expect(_testRecommendations(hasGold: true, hasLuci: true, hasCirrus: true), _Comparator.post);
+    expect(_testRecommendations(hasGold: true, hasLuci: true, hasFlutterRoot: true), _Comparator.post);
+    expect(_testRecommendations(hasGold: true, hasLuci: true, hasFlutterRoot: true, hasCirrus: true), _Comparator.post);
+
+    // On Luci, with Gold, pre-submit. Flutter root and Cirrus variables should have no effect.
+    expect(_testRecommendations(hasGold: true, hasLuci: true, hasTryJob: true), _Comparator.pre);
+    expect(_testRecommendations(hasGold: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.pre);
+    expect(_testRecommendations(hasGold: true, hasLuci: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.pre);
+    expect(_testRecommendations(hasGold: true, hasLuci: true, hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.pre);
+
+    // On Cirrus (with Gold and not on Luci), we skip regardless.
+    expect(_testRecommendations(hasCirrus: true, hasGold: true, hasFlutterRoot: true), _Comparator.skip);
+    expect(_testRecommendations(hasCirrus: true, hasGold: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.skip);
+  });
+
+  test('Comparator recommendations - release branch', () {
+    // If we're running locally (no CI), use a local comparator.
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0'), _Comparator.local);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true), _Comparator.local);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true), _Comparator.local);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasGold: true), _Comparator.local);
+
+    // If we don't have gold but are on CI, we skip regardless.
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasLuci: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasLuci: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasLuci: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasLuci: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasLuci: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasLuci: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+
+    // On Luci, with Gold, post-submit. Flutter root and Cirrus variables should have no effect. Branch should make us skip.
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true, hasFlutterRoot: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true, hasFlutterRoot: true, hasCirrus: true), _Comparator.skip);
+
+    // On Luci, with Gold, pre-submit. Flutter root and Cirrus variables should have no effect. Branch should make us skip.
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true, hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+
+    // On Cirrus (with Gold and not on Luci), we skip regardless.
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasCirrus: true, hasGold: true, hasFlutterRoot: true), _Comparator.skip);
+    expect(_testRecommendations(branch: 'flutter-3.16-candidate.0', hasCirrus: true, hasGold: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.skip);
+  });
+
+  test('Comparator recommendations - Linux', () {
+    // If we're running locally (no CI), use a local comparator.
+    expect(_testRecommendations(os: 'linux'), _Comparator.local);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true), _Comparator.local);
+    expect(_testRecommendations(os: 'linux', hasGold: true), _Comparator.local);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasGold: true), _Comparator.local);
+
+    // If we don't have gold but are on CI, we skip regardless.
+    expect(_testRecommendations(os: 'linux', hasLuci: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasLuci: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasLuci: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasCirrus: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
+
+    // On Luci, with Gold, post-submit. Flutter root and Cirrus variables should have no effect.
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true), _Comparator.post);
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasCirrus: true), _Comparator.post);
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasFlutterRoot: true), _Comparator.post);
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasFlutterRoot: true, hasCirrus: true), _Comparator.post);
+
+    // On Luci, with Gold, pre-submit. Flutter root and Cirrus variables should have no effect.
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasTryJob: true), _Comparator.pre);
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.pre);
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.pre);
+    expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.pre);
+
+    // On Cirrus (with Gold and not on Luci), we skip regardless.
+    expect(_testRecommendations(os: 'linux', hasCirrus: true, hasGold: true, hasFlutterRoot: true), _Comparator.skip);
+    expect(_testRecommendations(os: 'linux', hasCirrus: true, hasGold: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.skip);
+  });
+}

packages/flutter_goldens/test/flutter_goldens_test.dart

@@ -5,13 +5,14 @@
 // See also dev/automated_tests/flutter_test/flutter_gold_test.dart
 
 import 'dart:convert';
-import 'dart:io' hide Directory;
+import 'dart:io' as io;
 
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter_goldens/flutter_goldens.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:path/path.dart' as path;
 import 'package:platform/platform.dart';
 import 'package:process/process.dart';
 
@@ -27,1143 +28,962 @@ const List<int> _kTestPngBytes = <int>[
   78, 68, 174, 66, 96, 130,
 ];
 
+FileSystem createFakeFileSystem() {
+  return MemoryFileSystem()
+    ..directory(_kFlutterRoot).createSync(recursive: true);
+}
+
+(FileSystem, Directory) createFakeFileSystemWithWorkDirectory() {
+  final FileSystem fs = createFakeFileSystem();
+  final Directory workDirectory = fs.directory('/workDirectory')..createSync(recursive: true);
+  return (fs, workDirectory);
+}
+
+(FileSystem, Directory) createFakeFileSystemWithLibDirectory() {
+  final FileSystem fs = createFakeFileSystem();
+  final Directory lib = fs.directory('$_kFlutterRoot/test/library/')..createSync(recursive: true);
+  return (fs, lib);
+}
+
 void main() {
-  late MemoryFileSystem fs;
-  late FakePlatform platform;
-  late FakeProcessManager process;
-  late FakeHttpClient fakeHttpClient;
-
-  setUp(() {
-    fs = MemoryFileSystem();
-    platform = FakePlatform(
+  test('SkiaGoldClient - web HTML test', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'GOLDCTL': 'goldctl',
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'FLUTTER_TEST_BROWSER': 'Chrome',
+        'FLUTTER_WEB_RENDERER': 'html',
+      },
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final FakeProcessManager process = FakeProcessManager();
+    final io.HttpClient httpClient = ThrowingHttpClient();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: httpClient,
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    final File goldenFile = workDirectory.childFile('temp/golden_file_test.png')
+      ..createSync(recursive: true);
+
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'add',
+        '--work-dir', '/workDirectory/temp',
+        '--test-name', 'golden_file_test',
+        '--png-file', '/workDirectory/temp/golden_file_test.png',
+        '--passfail',
+        '--add-test-optional-key', 'image_matching_algorithm:fuzzy',
+        '--add-test-optional-key', 'fuzzy_max_different_pixels:20',
+        '--add-test-optional-key', 'fuzzy_pixel_delta_threshold:4',
+      ],
+      null,
+    );
+    process.processResults[goldctlInvocation] = io.ProcessResult(123, 0, '', '');
+    await skiaClient.imgtestAdd('golden_file_test.png', goldenFile);
+  });
+
+  test('SkiaGoldClient - web CanvasKit test', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'GOLDCTL': 'goldctl',
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'FLUTTER_TEST_BROWSER': 'Chrome',
+        'FLUTTER_WEB_RENDERER': 'canvaskit',
+      },
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final FakeProcessManager process = FakeProcessManager();
+    final io.HttpClient httpClient = FakeHttpClient();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: httpClient,
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    final File goldenFile = workDirectory.childFile('temp/golden_file_test.png')
+      ..createSync(recursive: true);
+
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'add',
+        '--work-dir', '/workDirectory/temp',
+        '--test-name', 'golden_file_test',
+        '--png-file', '/workDirectory/temp/golden_file_test.png',
+        '--passfail',
+      ],
+      null,
+    );
+    process.processResults[goldctlInvocation] = io.ProcessResult(123, 0, '', '');
+
+    await skiaClient.imgtestAdd('golden_file_test.png', goldenFile);
+  });
+
+  test('SkiaGoldClient - auth performs minimal work if already authorized', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final FakeProcessManager process = FakeProcessManager();
+    final File authFile = workDirectory.childFile('temp/auth_opt.json')
+      ..createSync(recursive: true);
+    authFile.writeAsStringSync(authTemplate());
+    process.fallbackProcessResult = io.ProcessResult(123, 0, '', '');
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    await skiaClient.auth();
+    expect(process.workingDirectories, isEmpty);
+  });
+
+  test('SkiaGoldClient - gsutil is checked when authorization file is present', () async {
+    final Platform platform = FakePlatform(
       environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
       operatingSystem: 'macos'
     );
-    process = FakeProcessManager();
-    fakeHttpClient = FakeHttpClient();
-    fs.directory(_kFlutterRoot).createSync(recursive: true);
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final ProcessManager process = FakeProcessManager();
+    final File authFile = workDirectory.childFile('temp/auth_opt.json')
+      ..createSync(recursive: true);
+    authFile.writeAsStringSync(authTemplate(gsutil: true));
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    expect(
+      await skiaClient.clientIsAuthorized(),
+      isFalse,
+    );
+  });
+
+  test('SkiaGoldClient - throws for error state from auth', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLD_SERVICE_ACCOUNT': 'Service Account',
+        'GOLDCTL': 'goldctl',
+      },
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final FakeProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    process.fallbackProcessResult = io.ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
+    expect(
+      skiaClient.auth(),
+      throwsException,
+    );
+  });
+
+  test('SkiaGoldClient - throws for error state from init', () {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'goldctl',
+      },
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final FakeProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    const RunInvocation gitInvocation = RunInvocation(
+      <String>['git', 'rev-parse', 'HEAD'],
+      '/flutter',
+    );
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'init',
+        '--instance', 'flutter',
+        '--work-dir', '/workDirectory/temp',
+        '--commit', '12345678',
+        '--keys-file', '/workDirectory/keys.json',
+        '--failure-file', '/workDirectory/failures.json',
+        '--passfail',
+      ],
+      null,
+    );
+    process.processResults[gitInvocation] = io.ProcessResult(12345678, 0, '12345678', '');
+    process.processResults[goldctlInvocation] = io.ProcessResult(123, 1, 'Expected failure', 'Expected failure');
+    process.fallbackProcessResult = io.ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
+
+    expect(
+      skiaClient.imgtestInit(),
+      throwsException,
+    );
+  });
+
+  test('SkiaGoldClient - Only calls init once', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'goldctl',
+      },
+      operatingSystem: 'macos',
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final FakeProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    const RunInvocation gitInvocation = RunInvocation(
+      <String>['git', 'rev-parse', 'HEAD'],
+      '/flutter',
+    );
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'init',
+        '--instance', 'flutter',
+        '--work-dir', '/workDirectory/temp',
+        '--commit', '1234',
+        '--keys-file', '/workDirectory/keys.json',
+        '--failure-file', '/workDirectory/failures.json',
+        '--passfail',
+      ],
+      null,
+    );
+    process.processResults[gitInvocation] = io.ProcessResult(1234, 0, '1234', '');
+    process.processResults[goldctlInvocation] = io.ProcessResult(5678, 0, '5678', '');
+    process.fallbackProcessResult = io.ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
+
+    // First call
+    await skiaClient.imgtestInit();
+
+    // Remove fake process result.
+    // If the init call is executed again, the fallback process will throw.
+    process.processResults.remove(goldctlInvocation);
+
+    // Second call
+    await skiaClient.imgtestInit();
+  });
+
+  test('SkiaGoldClient - Only calls tryjob init once', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'goldctl',
+        'SWARMING_TASK_ID': '4ae997b50dfd4d11',
+        'LOGDOG_STREAM_PREFIX': 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
+        'GOLD_TRYJOB': 'refs/pull/49815/head',
+      },
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final FakeProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    const RunInvocation gitInvocation = RunInvocation(
+      <String>['git', 'rev-parse', 'HEAD'],
+      '/flutter',
+    );
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'init',
+        '--instance', 'flutter',
+        '--work-dir', '/workDirectory/temp',
+        '--commit', '1234',
+        '--keys-file', '/workDirectory/keys.json',
+        '--failure-file', '/workDirectory/failures.json',
+        '--passfail',
+        '--crs', 'github',
+        '--patchset_id', '1234',
+        '--changelist', '49815',
+        '--cis', 'buildbucket',
+        '--jobid', '8885996262141582672',
+      ],
+      null,
+    );
+    process.processResults[gitInvocation] = io.ProcessResult(1234, 0, '1234', '');
+    process.processResults[goldctlInvocation] = io.ProcessResult(5678, 0, '5678', '');
+    process.fallbackProcessResult = io.ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
+
+    // First call
+    await skiaClient.tryjobInit();
+
+    // Remove fake process result.
+    // If the init call is executed again, the fallback process will throw.
+    process.processResults.remove(goldctlInvocation);
+
+    // Second call
+    await skiaClient.tryjobInit();
   });
 
-  group('SkiaGoldClient', () {
-    late SkiaGoldClient skiaClient;
-    late Directory workDirectory;
-
-    setUp(() {
-      workDirectory = fs.directory('/workDirectory')
-        ..createSync(recursive: true);
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-    });
-
-    test('web HTML test', () async {
-      platform = FakePlatform(
+  test('SkiaGoldClient - throws for error state from imgtestAdd', () {
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final File goldenFile = workDirectory.childFile('temp/golden_file_test.png')
+      ..createSync(recursive: true);
+    final FakeProcessManager process = FakeProcessManager();
+    final Platform platform = FakePlatform(
         environment: <String, String>{
-          'GOLDCTL': 'goldctl',
           'FLUTTER_ROOT': _kFlutterRoot,
-          'FLUTTER_TEST_BROWSER': 'Chrome',
-          'FLUTTER_WEB_RENDERER': 'html',
-        },
-        operatingSystem: 'macos'
-      );
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      final File goldenFile = fs.file('/workDirectory/temp/golden_file_test.png')
-        ..createSync(recursive: true);
-
-      const RunInvocation goldctlInvocation = RunInvocation(
-        <String>[
-          'goldctl',
-          'imgtest', 'add',
-          '--work-dir', '/workDirectory/temp',
-          '--test-name', 'golden_file_test',
-          '--png-file', '/workDirectory/temp/golden_file_test.png',
-          '--passfail',
-          '--add-test-optional-key', 'image_matching_algorithm:fuzzy',
-          '--add-test-optional-key', 'fuzzy_max_different_pixels:20',
-          '--add-test-optional-key', 'fuzzy_pixel_delta_threshold:4',
-        ],
-        null,
-      );
-      process.processResults[goldctlInvocation] = ProcessResult(123, 0, '', '');
-
-      expect(
-        await skiaClient.imgtestAdd('golden_file_test.png', goldenFile),
-        isTrue,
-      );
-    });
-
-    test('web CanvasKit test', () async {
-      platform = FakePlatform(
-        environment: <String, String>{
           'GOLDCTL': 'goldctl',
-          'FLUTTER_ROOT': _kFlutterRoot,
-          'FLUTTER_TEST_BROWSER': 'Chrome',
-          'FLUTTER_WEB_RENDERER': 'canvaskit',
         },
-        operatingSystem: 'macos'
-      );
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      final File goldenFile = fs.file('/workDirectory/temp/golden_file_test.png')
-        ..createSync(recursive: true);
-
-      const RunInvocation goldctlInvocation = RunInvocation(
-        <String>[
-          'goldctl',
-          'imgtest', 'add',
-          '--work-dir', '/workDirectory/temp',
-          '--test-name', 'golden_file_test',
-          '--png-file', '/workDirectory/temp/golden_file_test.png',
-          '--passfail',
-        ],
-        null,
-      );
-      process.processResults[goldctlInvocation] = ProcessResult(123, 0, '', '');
-
-      expect(
-        await skiaClient.imgtestAdd('golden_file_test.png', goldenFile),
-        isTrue,
-      );
-    });
-
-    test('auth performs minimal work if already authorized', () async {
-      final File authFile = fs.file('/workDirectory/temp/auth_opt.json')
-        ..createSync(recursive: true);
-      authFile.writeAsStringSync(authTemplate());
-      process.fallbackProcessResult = ProcessResult(123, 0, '', '');
-      await skiaClient.auth();
-
-      expect(process.workingDirectories, isEmpty);
-    });
-
-    test('gsutil is checked when authorization file is present', () async {
-      final File authFile = fs.file('/workDirectory/temp/auth_opt.json')
-        ..createSync(recursive: true);
-      authFile.writeAsStringSync(authTemplate(gsutil: true));
-      expect(
-        await skiaClient.clientIsAuthorized(),
-        isFalse,
-      );
-    });
-
-    test('throws for error state from auth', () async {
-      platform = FakePlatform(
-        environment: <String, String>{
-          'FLUTTER_ROOT': _kFlutterRoot,
-          'GOLD_SERVICE_ACCOUNT' : 'Service Account',
-          'GOLDCTL' : 'goldctl',
-        },
-        operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      process.fallbackProcessResult = ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
-
-      expect(
-        skiaClient.auth(),
-        throwsException,
-      );
-    });
-
-    test('throws for error state from init', () {
-      platform = FakePlatform(
-        environment: <String, String>{
-          'FLUTTER_ROOT': _kFlutterRoot,
-          'GOLDCTL' : 'goldctl',
-        },
-        operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      const RunInvocation gitInvocation = RunInvocation(
-        <String>['git', 'rev-parse', 'HEAD'],
-        '/flutter',
-      );
-      const RunInvocation goldctlInvocation = RunInvocation(
-        <String>[
-          'goldctl',
-          'imgtest', 'init',
-          '--instance', 'flutter',
-          '--work-dir', '/workDirectory/temp',
-          '--commit', '12345678',
-          '--keys-file', '/workDirectory/keys.json',
-          '--failure-file', '/workDirectory/failures.json',
-          '--passfail',
-        ],
-        null,
-      );
-      process.processResults[gitInvocation] = ProcessResult(12345678, 0, '12345678', '');
-      process.processResults[goldctlInvocation] = ProcessResult(123, 1, 'Expected failure', 'Expected failure');
-      process.fallbackProcessResult = ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
-
-      expect(
-        skiaClient.imgtestInit(),
-        throwsException,
-      );
-    });
-
-    test('Only calls init once', () async {
-      platform = FakePlatform(
-        environment: <String, String>{
-          'FLUTTER_ROOT': _kFlutterRoot,
-          'GOLDCTL' : 'goldctl',
-        },
-        operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      const RunInvocation gitInvocation = RunInvocation(
-        <String>['git', 'rev-parse', 'HEAD'],
-        '/flutter',
-      );
-      const RunInvocation goldctlInvocation = RunInvocation(
-        <String>[
-          'goldctl',
-          'imgtest', 'init',
-          '--instance', 'flutter',
-          '--work-dir', '/workDirectory/temp',
-          '--commit', '1234',
-          '--keys-file', '/workDirectory/keys.json',
-          '--failure-file', '/workDirectory/failures.json',
-          '--passfail',
-        ],
-        null,
-      );
-      process.processResults[gitInvocation] = ProcessResult(1234, 0, '1234', '');
-      process.processResults[goldctlInvocation] = ProcessResult(5678, 0, '5678', '');
-      process.fallbackProcessResult = ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
+        operatingSystem: 'macos',
+    );
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'add',
+        '--work-dir', '/workDirectory/temp',
+        '--test-name', 'golden_file_test',
+        '--png-file', '/workDirectory/temp/golden_file_test.png',
+        '--passfail',
+      ],
+      null,
+    );
+    process.processResults[goldctlInvocation] = io.ProcessResult(123, 1, 'Expected failure', 'Expected failure');
+    process.fallbackProcessResult = io.ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
 
-      // First call
-      await skiaClient.imgtestInit();
+    expect(
+      skiaClient.imgtestAdd('golden_file_test', goldenFile),
+      throwsException,
+    );
+  });
 
-      // Remove fake process result.
-      // If the init call is executed again, the fallback process will throw.
-      process.processResults.remove(goldctlInvocation);
+  test('SkiaGoldClient - correctly inits tryjob for luci', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'goldctl',
+        'SWARMING_TASK_ID': '4ae997b50dfd4d11',
+        'LOGDOG_STREAM_PREFIX': 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
+        'GOLD_TRYJOB': 'refs/pull/49815/head',
+      },
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final ProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
 
-      // Second call
-      await skiaClient.imgtestInit();
-    });
+    final List<String> ciArguments = skiaClient.getCIArguments();
 
-    test('Only calls tryjob init once', () async {
-      platform = FakePlatform(
-        environment: <String, String>{
-          'FLUTTER_ROOT': _kFlutterRoot,
-          'GOLDCTL' : 'goldctl',
-          'SWARMING_TASK_ID' : '4ae997b50dfd4d11',
-          'LOGDOG_STREAM_PREFIX' : 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
-          'GOLD_TRYJOB' : 'refs/pull/49815/head',
-        },
-        operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      const RunInvocation gitInvocation = RunInvocation(
-        <String>['git', 'rev-parse', 'HEAD'],
-        '/flutter',
-      );
-      const RunInvocation goldctlInvocation = RunInvocation(
+    expect(
+      ciArguments,
+      equals(
         <String>[
-          'goldctl',
-          'imgtest', 'init',
-          '--instance', 'flutter',
-          '--work-dir', '/workDirectory/temp',
-          '--commit', '1234',
-          '--keys-file', '/workDirectory/keys.json',
-          '--failure-file', '/workDirectory/failures.json',
-          '--passfail',
-          '--crs', 'github',
-          '--patchset_id', '1234',
           '--changelist', '49815',
           '--cis', 'buildbucket',
           '--jobid', '8885996262141582672',
         ],
-        null,
-      );
-      process.processResults[gitInvocation] = ProcessResult(1234, 0, '1234', '');
-      process.processResults[goldctlInvocation] = ProcessResult(5678, 0, '5678', '');
-      process.fallbackProcessResult = ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
-
-      // First call
-      await skiaClient.tryjobInit();
-
-      // Remove fake process result.
-      // If the init call is executed again, the fallback process will throw.
-      process.processResults.remove(goldctlInvocation);
-
-      // Second call
-      await skiaClient.tryjobInit();
-    });
-
-    test('throws for error state from imgtestAdd', () {
-      final File goldenFile = fs.file('/workDirectory/temp/golden_file_test.png')
-        ..createSync(recursive: true);
-      platform = FakePlatform(
-          environment: <String, String>{
-            'FLUTTER_ROOT': _kFlutterRoot,
-            'GOLDCTL' : 'goldctl',
-          },
-          operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      const RunInvocation goldctlInvocation = RunInvocation(
-        <String>[
-          'goldctl',
-          'imgtest', 'add',
-          '--work-dir', '/workDirectory/temp',
-          '--test-name', 'golden_file_test',
-          '--png-file', '/workDirectory/temp/golden_file_test.png',
-          '--passfail',
-        ],
-        null,
-      );
-      process.processResults[goldctlInvocation] = ProcessResult(123, 1, 'Expected failure', 'Expected failure');
-      process.fallbackProcessResult = ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
-
-      expect(
-        skiaClient.imgtestAdd('golden_file_test', goldenFile),
-        throwsException,
-      );
-    });
-
-    test('correctly inits tryjob for luci', () async {
-      platform = FakePlatform(
+      ),
+    );
+  });
+
+  test('SkiaGoldClient - Creates traceID correctly - Linux', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'goldctl',
+        'SWARMING_TASK_ID': '4ae997b50dfd4d11',
+        'LOGDOG_STREAM_PREFIX': 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
+        'GOLD_TRYJOB': 'refs/pull/49815/head',
+      },
+      operatingSystem: 'linux',
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final ProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    expect(
+      skiaClient.getTraceID('flutter.golden.1'),
+      equals('ae18c7a6aa48e0685525dfe8fdf79003'),
+    );
+  });
+
+  test('SkiaGoldClient - Creates traceID correctly - Linux web', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'goldctl',
+        'SWARMING_TASK_ID': '4ae997b50dfd4d11',
+        'LOGDOG_STREAM_PREFIX': 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
+        'GOLD_TRYJOB': 'refs/pull/49815/head',
+        'FLUTTER_TEST_BROWSER': 'chrome', // flips browser bit
+      },
+      operatingSystem: 'linux',
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final ProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    expect(
+      skiaClient.getTraceID('flutter.golden.1'),
+      equals('e9d5c296c48e7126808520e9cc191243'),
+    );
+  });
+
+  test('SkiaGoldClient - Creates traceID correctly - Linux', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'goldctl',
+        'SWARMING_TASK_ID': '4ae997b50dfd4d11',
+        'LOGDOG_STREAM_PREFIX': 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
+        'GOLD_TRYJOB': 'refs/pull/49815/head',
+      },
+      operatingSystem: 'macos', // different operating system
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final ProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    expect(
+      skiaClient.getTraceID('flutter.golden.1'),
+      equals('9968695b9ae78cdb77cbb2be621ca2d6'),
+    );
+  });
+
+  test('SkiaGoldClient - throws for error state from imgtestAdd', () {
+    final Platform platform = FakePlatform(
         environment: <String, String>{
           'FLUTTER_ROOT': _kFlutterRoot,
-          'GOLDCTL' : 'goldctl',
-          'SWARMING_TASK_ID' : '4ae997b50dfd4d11',
-          'LOGDOG_STREAM_PREFIX' : 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
-          'GOLD_TRYJOB' : 'refs/pull/49815/head',
+          'GOLDCTL': 'goldctl',
         },
-        operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      final List<String> ciArguments = skiaClient.getCIArguments();
-
-      expect(
-        ciArguments,
-        equals(
-          <String>[
-            '--changelist', '49815',
-            '--cis', 'buildbucket',
-            '--jobid', '8885996262141582672',
-          ],
+        operatingSystem: 'macos',
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final File goldenFile = workDirectory.childFile('temp/golden_file_test.png')
+      ..createSync(recursive: true);
+    final FakeProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'add',
+        '--work-dir', '/workDirectory/temp',
+        '--test-name', 'golden_file_test',
+        '--png-file', '/workDirectory/temp/golden_file_test.png',
+        '--passfail',
+      ],
+      null,
+    );
+    process.processResults[goldctlInvocation] = io.ProcessResult(123, 1, 'Expected failure', 'Expected failure');
+    process.fallbackProcessResult = io.ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
+
+    expect(
+      skiaClient.imgtestAdd('golden_file_test', goldenFile),
+      throwsA(
+        isA<SkiaException>().having((SkiaException error) => error.message,
+          'message',
+          'Golden test for "golden_file_test" failed for a reason unrelated to pixel comparison.\n'
+          '\n'
+          'imgtest add failed with exit code 1.\n'
+          '\n'
+          'stdout from gold:\n'
+          '  Fallback failure\n'
+          '\n'
+          'stderr from gold:\n'
+          '  Fallback failure\n',
         ),
-      );
-    });
+      ),
+    );
+  });
 
-    test('Creates traceID correctly', () async {
-      String traceID;
-      platform = FakePlatform(
-        environment: <String, String>{
-          'FLUTTER_ROOT': _kFlutterRoot,
-          'GOLDCTL' : 'goldctl',
-          'SWARMING_TASK_ID' : '4ae997b50dfd4d11',
-          'LOGDOG_STREAM_PREFIX' : 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
-          'GOLD_TRYJOB' : 'refs/pull/49815/head',
-        },
-        operatingSystem: 'linux'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      traceID = skiaClient.getTraceID('flutter.golden.1');
-      expect(
-        traceID,
-        equals('ae18c7a6aa48e0685525dfe8fdf79003'),
-      );
-
-      // Browser
-      platform = FakePlatform(
-        environment: <String, String>{
-          'FLUTTER_ROOT': _kFlutterRoot,
-          'GOLDCTL' : 'goldctl',
-          'SWARMING_TASK_ID' : '4ae997b50dfd4d11',
-          'LOGDOG_STREAM_PREFIX' : 'buildbucket/cr-buildbucket.appspot.com/8885996262141582672',
-          'GOLD_TRYJOB' : 'refs/pull/49815/head',
-          'FLUTTER_TEST_BROWSER' : 'chrome',
-        },
-        operatingSystem: 'linux'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      traceID = skiaClient.getTraceID('flutter.golden.1');
-      expect(
-        traceID,
-        equals('e9d5c296c48e7126808520e9cc191243'),
-      );
-
-      // Locally - should defer to luci traceID
-      platform = FakePlatform(
+  test('SkiaGoldClient - throws for error state from tryjobAdd', () {
+    final Platform platform = FakePlatform(
         environment: <String, String>{
           'FLUTTER_ROOT': _kFlutterRoot,
+          'GOLDCTL': 'goldctl',
         },
-        operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      traceID = skiaClient.getTraceID('flutter.golden.1');
-      expect(
-        traceID,
-        equals('9968695b9ae78cdb77cbb2be621ca2d6'),
-      );
-    });
-
-    test('throws for error state from imgtestAdd', () {
-      final File goldenFile = fs.file('/workDirectory/temp/golden_file_test.png')
-        ..createSync(recursive: true);
-      platform = FakePlatform(
-          environment: <String, String>{
-            'FLUTTER_ROOT': _kFlutterRoot,
-            'GOLDCTL' : 'goldctl',
-          },
-          operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      const RunInvocation goldctlInvocation = RunInvocation(
-        <String>[
-          'goldctl',
-          'imgtest', 'add',
-          '--work-dir', '/workDirectory/temp',
-          '--test-name', 'golden_file_test',
-          '--png-file', '/workDirectory/temp/golden_file_test.png',
-          '--passfail',
-        ],
-        null,
-      );
-      process.processResults[goldctlInvocation] = ProcessResult(123, 1, 'Expected failure', 'Expected failure');
-      process.fallbackProcessResult = ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
-
-      expect(
-          skiaClient.imgtestAdd('golden_file_test', goldenFile),
-        throwsA(
-          isA<SkiaException>().having((SkiaException error) => error.message,
-            'message',
-            contains('result-state.json'),
-          ),
-        ),
-      );
-    });
-
-    test('throws for error state from tryjobAdd', () {
-      final File goldenFile = fs.file('/workDirectory/temp/golden_file_test.png')
-        ..createSync(recursive: true);
-      platform = FakePlatform(
-          environment: <String, String>{
-            'FLUTTER_ROOT': _kFlutterRoot,
-            'GOLDCTL' : 'goldctl',
-          },
-          operatingSystem: 'macos'
-      );
-
-      skiaClient = SkiaGoldClient(
-        workDirectory,
-        fs: fs,
-        process: process,
-        platform: platform,
-        httpClient: fakeHttpClient,
-      );
-
-      const RunInvocation goldctlInvocation = RunInvocation(
-        <String>[
-          'goldctl',
-          'imgtest', 'add',
-          '--work-dir', '/workDirectory/temp',
-          '--test-name', 'golden_file_test',
-          '--png-file', '/workDirectory/temp/golden_file_test.png',
-          '--passfail',
-        ],
-        null,
-      );
-      process.processResults[goldctlInvocation] = ProcessResult(123, 1, 'Expected failure', 'Expected failure');
-      process.fallbackProcessResult = ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
-
-      expect(
-        skiaClient.tryjobAdd('golden_file_test', goldenFile),
-        throwsA(
-          isA<SkiaException>().having((SkiaException error) => error.message,
-            'message',
-            contains('result-state.json'),
-          ),
+        operatingSystem: 'macos',
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final File goldenFile = workDirectory.childFile('temp/golden_file_test.png')
+      ..createSync(recursive: true);
+    final FakeProcessManager process = FakeProcessManager();
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+
+    const RunInvocation goldctlInvocation = RunInvocation(
+      <String>[
+        'goldctl',
+        'imgtest', 'add',
+        '--work-dir', '/workDirectory/temp',
+        '--test-name', 'golden_file_test',
+        '--png-file', '/workDirectory/temp/golden_file_test.png',
+        '--passfail',
+      ],
+      null,
+    );
+    process.processResults[goldctlInvocation] = io.ProcessResult(123, 1, 'Expected failure', 'Expected failure');
+    process.fallbackProcessResult = io.ProcessResult(123, 1, 'Fallback failure', 'Fallback failure');
+
+    expect(
+      skiaClient.tryjobAdd('golden_file_test', goldenFile),
+      throwsA(
+        isA<SkiaException>().having((SkiaException error) => error.message,
+          'message',
+          'Golden test for "golden_file_test" failed for a reason unrelated to pixel comparison.\n'
+          '\n'
+          'imgtest add failed with exit code 1.\n'
+          '\n'
+          'stdout from gold:\n'
+          '  Fallback failure\n'
+          '\n'
+          'stderr from gold:\n'
+          '  Fallback failure\n',
         ),
-      );
-    });
+      ),
+    );
+  });
 
-    group('Request Handling', () {
-      const String expectation = '55109a4bed52acc780530f7a9aeff6c0';
+  test('SkiaGoldClient - Request Handling - image bytes are processed properly', () async {
+    const String expectation = '55109a4bed52acc780530f7a9aeff6c0';
+    final Platform platform = FakePlatform(
+      environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory workDirectory) = createFakeFileSystemWithWorkDirectory();
+    final ProcessManager process = FakeProcessManager();
+    final Uri imageUrl = Uri.parse(
+      'https://flutter-gold.skia.org/img/images/$expectation.png'
+    );
+    final FakeHttpClient fakeHttpClient = FakeHttpClient();
+    final FakeHttpClientRequest fakeImageRequest = FakeHttpClientRequest();
+    final FakeHttpImageResponse fakeImageResponse = FakeHttpImageResponse(
+      imageResponseTemplate()
+    );
 
-      test('image bytes are processed properly', () async {
-        final Uri imageUrl = Uri.parse(
-          'https://flutter-gold.skia.org/img/images/$expectation.png'
-        );
-        final FakeHttpClientRequest fakeImageRequest = FakeHttpClientRequest();
-        final FakeHttpImageResponse fakeImageResponse = FakeHttpImageResponse(
-          imageResponseTemplate()
-        );
+    fakeHttpClient.request = fakeImageRequest;
+    fakeImageRequest.response = fakeImageResponse;
 
-        fakeHttpClient.request = fakeImageRequest;
-        fakeImageRequest.response = fakeImageResponse;
+    final SkiaGoldClient skiaClient = SkiaGoldClient(
+      workDirectory,
+      fs: fs,
+      process: process,
+      platform: platform,
+      httpClient: fakeHttpClient,
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    final List<int> masterBytes = await skiaClient.getImageBytes(expectation);
 
-        final List<int> masterBytes = await skiaClient.getImageBytes(expectation);
+    expect(fakeHttpClient.lastUri, imageUrl);
+    expect(masterBytes, equals(_kTestPngBytes));
+  });
 
-        expect(fakeHttpClient.lastUri, imageUrl);
-        expect(masterBytes, equals(_kTestPngBytes));
-      });
-    });
+  test('FlutterGoldenFileComparator - calculates the basedir correctly from defaultComparator for local testing', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+      operatingSystem: 'macos'
+    );
+    final FileSystem fs = createFakeFileSystem();
+    final FakeLocalFileComparator defaultComparator = FakeLocalFileComparator();
+    final Directory flutterRoot = fs.directory(platform.environment['FLUTTER_ROOT'])
+      ..createSync(recursive: true);
+    defaultComparator.basedir = flutterRoot.childDirectory('baz').uri;
+
+    final Directory basedir = FlutterGoldenFileComparator.getBaseDirectory(
+      defaultComparator,
+      platform: platform,
+      fs: fs,
+    );
+    expect(
+      basedir.uri,
+      fs.directory('/flutter/bin/cache/pkg/skia_goldens/baz').uri,
+    );
   });
 
-  group('FlutterGoldenFileComparator', () {
-    late FlutterGoldenFileComparator comparator;
-
-    setUp(() {
-      final Directory basedir = fs.directory('flutter/test/library/')
-        ..createSync(recursive: true);
-      comparator = FlutterPostSubmitFileComparator(
-        basedir.uri,
-        FakeSkiaGoldClient(),
-        fs: fs,
-        platform: platform,
-      );
-    });
-
-    test('calculates the basedir correctly from defaultComparator for local testing', () async {
-      final FakeLocalFileComparator defaultComparator = FakeLocalFileComparator();
-      final Directory flutterRoot = fs.directory(platform.environment['FLUTTER_ROOT'])
-        ..createSync(recursive: true);
-      defaultComparator.basedir = flutterRoot.childDirectory('baz').uri;
-
-      final Directory basedir = FlutterGoldenFileComparator.getBaseDirectory(
-        defaultComparator,
-        platform,
-      );
-      expect(
-        basedir.uri,
-        fs.directory('/flutter/bin/cache/pkg/skia_goldens/baz').uri,
-      );
-    });
-
-    test('ignores version number', () {
-      final Uri key = comparator.getTestUri(Uri.parse('foo.png'), 1);
-      expect(key, Uri.parse('foo.png'));
-    });
-
-    test('adds namePrefix', () async {
-      const String libraryName = 'sidedishes';
-      const String namePrefix = 'tomatosalad';
-      const String fileName = 'lettuce.png';
-      final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
-      final Directory basedir = fs.directory('flutter/test/$libraryName/')
-        ..createSync(recursive: true);
-      final FlutterGoldenFileComparator comparator = FlutterPostSubmitFileComparator(
-        basedir.uri,
-        fakeSkiaClient,
-        fs: fs,
-        platform: platform,
-        namePrefix: namePrefix,
-      );
-      await comparator.compare(
-        Uint8List.fromList(_kTestPngBytes),
-        Uri.parse(fileName),
-      );
-      expect(fakeSkiaClient.testNames.single, '$namePrefix.$libraryName.$fileName');
-    });
-
-    group('Post-Submit', () {
-      late FakeSkiaGoldClient fakeSkiaClient;
-
-      setUp(() {
-        fakeSkiaClient = FakeSkiaGoldClient();
-        final Directory basedir = fs.directory('flutter/test/library/')
-          ..createSync(recursive: true);
-        comparator = FlutterPostSubmitFileComparator(
-          basedir.uri,
-          fakeSkiaClient,
-          fs: fs,
-          platform: platform,
-        );
-      });
-
-      test('asserts .png format', () async {
-        await expectLater(
-          () async {
-            return comparator.compare(
-              Uint8List.fromList(_kTestPngBytes),
-              Uri.parse('flutter.golden_test.1'),
-            );
-          },
-          throwsA(
-            isA<AssertionError>().having((AssertionError error) => error.toString(),
-              'description',
-              contains(
-                'Golden files in the Flutter framework must end with the file '
-                'extension .png.'
-              ),
-            ),
-          ),
-        );
-      });
+  test('FlutterGoldenFileComparator - ignores version number', () {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory libDirectory) = createFakeFileSystemWithLibDirectory();
+    final List<String> log = <String>[];
+    final FlutterGoldenFileComparator comparator = FlutterPostSubmitFileComparator(
+      libDirectory.uri,
+      FakeSkiaGoldClient(),
+      fs: fs,
+      platform: platform,
+      log: log.add,
+    );
+    final Uri key = comparator.getTestUri(Uri.parse('foo.png'), 1);
+    expect(key, Uri.parse('foo.png'));
+    expect(log, isEmpty);
+  });
 
-      test('calls init during compare', () {
-        expect(fakeSkiaClient.initCalls, 0);
-        comparator.compare(
+  test('FlutterGoldenFileComparator - adds namePrefix', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+      operatingSystem: 'macos'
+    );
+    const String libraryName = 'sidedishes';
+    const String namePrefix = 'tomatosalad';
+    const String fileName = 'lettuce.png';
+    final FileSystem fs = createFakeFileSystem();
+    final Directory basedir = fs.directory('flutter/test/$libraryName/')
+      ..createSync(recursive: true);
+    final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+    final List<String> log = <String>[];
+    final FlutterGoldenFileComparator comparator = FlutterPostSubmitFileComparator(
+      basedir.uri,
+      fakeSkiaClient,
+      fs: fs,
+      platform: platform,
+      log: log.add,
+      namePrefix: namePrefix,
+    );
+    await comparator.compare(
+      Uint8List.fromList(_kTestPngBytes),
+      Uri.parse(fileName),
+    );
+    expect(fakeSkiaClient.testNames.single, '$namePrefix.$libraryName.$fileName');
+    expect(log, isEmpty);
+  });
+
+  test('FlutterGoldenFileComparator - Post-Submit - asserts .png format', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory libDirectory) = createFakeFileSystemWithLibDirectory();
+    final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+    final List<String> log = <String>[];
+    final FlutterGoldenFileComparator comparator = FlutterPostSubmitFileComparator(
+      libDirectory.uri,
+      fakeSkiaClient,
+      fs: fs,
+      platform: platform,
+      log: log.add,
+    );
+    await expectLater(
+      () async {
+        return comparator.compare(
           Uint8List.fromList(_kTestPngBytes),
-          Uri.parse('flutter.golden_test.1.png'),
-        );
-        expect(fakeSkiaClient.initCalls, 1);
-      });
-
-      test('does not call init in during construction', () {
-        expect(fakeSkiaClient.initCalls, 0);
-        FlutterPostSubmitFileComparator.fromDefaultComparator(
-          platform,
-          goldens: fakeSkiaClient,
+          Uri.parse('flutter.golden_test.1'),
         );
-        expect(fakeSkiaClient.initCalls, 0);
-      });
-
-      group('correctly determines testing environment', () {
-        test('returns true for configured Luci', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : '12345678990',
-              'GOLDCTL' : 'goldctl',
-              'GIT_BRANCH' : 'master',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns false on release branches in postsubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GIT_BRANCH' : 'flutter-3.16-candidate.0',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-
-        test('returns true on master branch in postsubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GIT_BRANCH' : 'master',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns true on main branch in postsubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GIT_BRANCH' : 'main',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns false - GOLDCTL not present', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : '12345678990',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-
-        test('returns false - GOLD_TRYJOB active', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : '12345678990',
-              'GOLDCTL' : 'goldctl',
-              'GOLD_TRYJOB' : 'git/ref/12345/head',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-
-        test('returns false - on Cirrus', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'CIRRUS_CI': 'true',
-              'CIRRUS_PR': '',
-              'CIRRUS_BRANCH': 'master',
-              'GOLD_SERVICE_ACCOUNT': 'service account...',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-      });
-    });
-
-    group('Pre-Submit', () {
-      late FakeSkiaGoldClient fakeSkiaClient;
-
-      setUp(() {
-        fakeSkiaClient = FakeSkiaGoldClient();
-        final Directory basedir = fs.directory('flutter/test/library/')
-          ..createSync(recursive: true);
-        comparator = FlutterPreSubmitFileComparator(
-          basedir.uri,
-          fakeSkiaClient,
-          fs: fs,
-          platform: platform,
-        );
-      });
-
-      test('asserts .png format', () async {
-        await expectLater(
-          () async {
-            return comparator.compare(
-              Uint8List.fromList(_kTestPngBytes),
-              Uri.parse('flutter.golden_test.1'),
-            );
-          },
-          throwsA(
-            isA<AssertionError>().having((AssertionError error) => error.toString(),
-              'description',
-              contains(
-                'Golden files in the Flutter framework must end with the file '
-                'extension .png.'
-              ),
-            ),
+      },
+      throwsA(
+        isA<AssertionError>().having((AssertionError error) => error.toString(),
+          'description',
+          contains(
+            'Golden files in the Flutter framework must end with the file '
+            'extension .png.'
           ),
-        );
-      });
+        ),
+      ),
+    );
+    expect(log, isEmpty);
+  });
+
+  test('FlutterGoldenFileComparator - Post-Submit - calls init during compare', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+      operatingSystem: 'macos'
+    );
+    final (FileSystem fs, Directory libDirectory) = createFakeFileSystemWithLibDirectory();
+    final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+    final List<String> log = <String>[];
+    final FlutterGoldenFileComparator comparator = FlutterPostSubmitFileComparator(
+      libDirectory.uri,
+      fakeSkiaClient,
+      fs: fs,
+      platform: platform,
+      log: log.add,
+    );
+    expect(fakeSkiaClient.initCalls, 0);
+    await comparator.compare(
+      Uint8List.fromList(_kTestPngBytes),
+      Uri.parse('flutter.golden_test.1.png'),
+    );
+    expect(fakeSkiaClient.initCalls, 1);
+    expect(log, isEmpty);
+  });
 
-      test('calls init during compare', () {
-        expect(fakeSkiaClient.tryInitCalls, 0);
-        comparator.compare(
+  test('FlutterGoldenFileComparator - Post-Submit - does not call init in during construction', () {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'testctl',
+      },
+      operatingSystem: 'macos'
+    );
+    final FileSystem fs = createFakeFileSystem();
+    final List<String> log = <String>[];
+    FlutterPostSubmitFileComparator.fromLocalFileComparator(
+      localFileComparator: LocalFileComparator(Uri.parse('/test'), pathStyle: path.Style.posix),
+      platform: platform,
+      fs: fs,
+      process: LoggingProcessManager(log),
+      httpClient: ThrowingHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    expect(log, isEmpty);
+  });
+
+  test('FlutterGoldenFileComparator - Pre-Submit - asserts .png format', () async {
+    final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+    final (FileSystem fs, Directory libDirectory) = createFakeFileSystemWithLibDirectory();
+    final List<String> log = <String>[];
+    final FlutterGoldenFileComparator comparator = FlutterPreSubmitFileComparator(
+      libDirectory.uri,
+      fakeSkiaClient,
+      fs: fs,
+      platform: FakePlatform(
+        environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+        operatingSystem: 'macos',
+      ),
+      log: log.add,
+    );
+    await expectLater(
+      () async {
+        return comparator.compare(
           Uint8List.fromList(_kTestPngBytes),
-          Uri.parse('flutter.golden_test.1.png'),
-        );
-        expect(fakeSkiaClient.tryInitCalls, 1);
-      });
-
-      test('does not call init in during construction', () {
-        expect(fakeSkiaClient.tryInitCalls, 0);
-        FlutterPostSubmitFileComparator.fromDefaultComparator(
-          platform,
-          goldens: fakeSkiaClient,
+          Uri.parse('flutter.golden_test.1'),
         );
-        expect(fakeSkiaClient.tryInitCalls, 0);
-      });
-
-      group('correctly determines testing environment', () {
-        test('returns false on release branches in presubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GOLD_TRYJOB' : 'true',
-              'GIT_BRANCH' : 'flutter-3.16-candidate.0',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-
-        test('returns true on master branch in presubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GOLD_TRYJOB' : 'true',
-              'GIT_BRANCH' : 'master',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns true on main branch in presubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GOLD_TRYJOB' : 'true',
-              'GIT_BRANCH' : 'main',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns true for Luci', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : '12345678990',
-              'GOLDCTL' : 'goldctl',
-              'GOLD_TRYJOB' : 'git/ref/12345/head',
-              'GIT_BRANCH' : 'master',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns false - not on Luci', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-
-        test('returns false - GOLDCTL missing', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : '12345678990',
-              'GOLD_TRYJOB' : 'git/ref/12345/head',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-
-        test('returns false - GOLD_TRYJOB missing', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : '12345678990',
-              'GOLDCTL' : 'goldctl',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-
-        test('returns false - on Cirrus', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'CIRRUS_CI': 'true',
-              'CIRRUS_PR': '',
-              'CIRRUS_BRANCH': 'master',
-              'GOLD_SERVICE_ACCOUNT': 'service account...',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterPostSubmitFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-      });
-    });
-
-    group('Skipping', () {
-      group('correctly determines testing environment', () {
-        test('returns true on release branches in presubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GOLD_TRYJOB' : 'true',
-              'GIT_BRANCH' : 'flutter-3.16-candidate.0',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterSkippingFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns true on release branches in postsubmit', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : 'sweet task ID',
-              'GOLDCTL' : 'some/path',
-              'GIT_BRANCH' : 'flutter-3.16-candidate.0',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterSkippingFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns true on Cirrus builds', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'CIRRUS_CI' : 'yep',
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterSkippingFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns true on irrelevant LUCI builds', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-              'SWARMING_TASK_ID' : '1234567890',
-            },
-            operatingSystem: 'macos'
-          );
-          expect(
-            FlutterSkippingFileComparator.isAvailableForEnvironment(platform),
-            isTrue,
-          );
-        });
-
-        test('returns false - not in CI', () {
-          platform = FakePlatform(
-            environment: <String, String>{
-              'FLUTTER_ROOT': _kFlutterRoot,
-            },
-            operatingSystem: 'macos',
-          );
-          expect(
-            FlutterSkippingFileComparator.isAvailableForEnvironment(platform),
-            isFalse,
-          );
-        });
-      });
-    });
-
-    group('Local', () {
-      late FlutterLocalFileComparator comparator;
-      final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
-
-      setUp(() async {
-        final Directory basedir = fs.directory('flutter/test/library/')
-          ..createSync(recursive: true);
-        comparator = FlutterLocalFileComparator(
-          basedir.uri,
-          fakeSkiaClient,
-          fs: fs,
-          platform: FakePlatform(
-            environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
-            operatingSystem: 'macos',
+      },
+      throwsA(
+        isA<AssertionError>().having((AssertionError error) => error.toString(),
+          'description',
+          contains(
+            'Golden files in the Flutter framework must end with the file '
+            'extension .png.'
           ),
-        );
-
-        const String hash = '55109a4bed52acc780530f7a9aeff6c0';
-        fakeSkiaClient.expectationForTestValues['flutter.golden_test.1'] = hash;
-        fakeSkiaClient.imageBytesValues[hash] =_kTestPngBytes;
-        fakeSkiaClient.cleanTestNameValues['library.flutter.golden_test.1.png'] = 'flutter.golden_test.1';
-      });
-
-      test('asserts .png format', () async {
-        await expectLater(
-          () async {
-            return comparator.compare(
-              Uint8List.fromList(_kTestPngBytes),
-              Uri.parse('flutter.golden_test.1'),
-            );
-          },
-          throwsA(
-            isA<AssertionError>().having((AssertionError error) => error.toString(),
-              'description',
-              contains(
-                'Golden files in the Flutter framework must end with the file '
-                'extension .png.'
-              ),
-            ),
-          ),
-        );
-      });
+        ),
+      ),
+    );
+    expect(log, isEmpty);
+  });
 
-      test('passes when bytes match', () async {
-        expect(
-          await comparator.compare(
-            Uint8List.fromList(_kTestPngBytes),
-            Uri.parse('flutter.golden_test.1.png'),
-          ),
-          isTrue,
-        );
-      });
+  test('FlutterGoldenFileComparator - Pre-Submit - calls init during compare', () async {
+    final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+    final (FileSystem fs, Directory libDirectory) = createFakeFileSystemWithLibDirectory();
+    final List<String> log = <String>[];
+    final FlutterGoldenFileComparator comparator = FlutterPreSubmitFileComparator(
+      libDirectory.uri,
+      fakeSkiaClient,
+      fs: fs,
+      platform: FakePlatform(
+        environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+        operatingSystem: 'macos',
+      ),
+      log: log.add,
+    );
+    expect(fakeSkiaClient.tryInitCalls, 0);
+    await comparator.compare(
+      Uint8List.fromList(_kTestPngBytes),
+      Uri.parse('flutter.golden_test.1.png'),
+    );
+    expect(fakeSkiaClient.tryInitCalls, 1);
+    expect(log, isEmpty);
+  });
 
-      test('returns FlutterSkippingGoldenFileComparator when network connection is unavailable', () async {
-        final FakeDirectory fakeDirectory = FakeDirectory();
-        fakeDirectory.existsSyncValue = true;
-        fakeDirectory.uri = Uri.parse('/flutter');
+  test('FlutterGoldenFileComparator - Pre-Submit - does not call init in during construction', () async {
+    final Platform platform = FakePlatform(
+      environment: <String, String>{
+        'FLUTTER_ROOT': _kFlutterRoot,
+        'GOLDCTL': 'testctl',
+      },
+      operatingSystem: 'macos',
+    );
+    final FileSystem fs = createFakeFileSystem();
+    final List<String> log = <String>[];
+    await FlutterPostSubmitFileComparator.fromLocalFileComparator(
+      localFileComparator: LocalFileComparator(Uri.parse('/test'), pathStyle: path.Style.posix),
+      platform: platform,
+      fs: fs,
+      process: LoggingProcessManager(log),
+      httpClient: FakeHttpClient(),
+      log: (String message) => fail('skia gold client printed unexpected output: "$message"'),
+    );
+    expect(log, <String>['testctl auth --work-dir /.tmp_rand0/flutter_goldens_postsubmit.rand0/../temp --luci']);
+  });
 
-        fakeSkiaClient.getExpectationForTestThrowable = const OSError("Can't reach Gold");
+  test('FlutterGoldenFileComparator - Local - asserts .png format', () async {
+    final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+    final (FileSystem fs, Directory libDirectory) = createFakeFileSystemWithLibDirectory();
+    final List<String> log = <String>[];
+    final FlutterLocalFileComparator comparator = FlutterLocalFileComparator(
+      libDirectory.uri,
+      fakeSkiaClient,
+      fs: fs,
+      platform: FakePlatform(
+        environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+        operatingSystem: 'macos',
+      ),
+      log: log.add,
+    );
 
-        FlutterGoldenFileComparator comparator = await FlutterLocalFileComparator.fromDefaultComparator(
-          platform,
-          goldens: fakeSkiaClient,
-          baseDirectory: fakeDirectory,
+    const String hash = '55109a4bed52acc780530f7a9aeff6c0';
+    fakeSkiaClient.expectationForTestValues['flutter.golden_test.1'] = hash;
+    fakeSkiaClient.imageBytesValues[hash] =_kTestPngBytes;
+    fakeSkiaClient.cleanTestNameValues['library.flutter.golden_test.1.png'] = 'flutter.golden_test.1';
+    await expectLater(
+      () async {
+        return comparator.compare(
+          Uint8List.fromList(_kTestPngBytes),
+          Uri.parse('flutter.golden_test.1'),
         );
-        expect(comparator.runtimeType, FlutterSkippingFileComparator);
+      },
+      throwsA(
+        isA<AssertionError>().having((AssertionError error) => error.toString(),
+          'description',
+          contains(
+            'Golden files in the Flutter framework must end with the file '
+            'extension .png.'
+          ),
+        ),
+      ),
+    );
+    expect(log, isEmpty);
+  });
 
-        fakeSkiaClient.getExpectationForTestThrowable =  const SocketException("Can't reach Gold");
+  test('FlutterGoldenFileComparator - Local - passes when bytes match', () async {
+    final List<String> log = <String>[];
+    final FakeSkiaGoldClient fakeSkiaClient = FakeSkiaGoldClient();
+    final (FileSystem fs, Directory libDirectory) = createFakeFileSystemWithLibDirectory();
+    final FlutterLocalFileComparator comparator = FlutterLocalFileComparator(
+      libDirectory.uri,
+      fakeSkiaClient,
+      fs: fs,
+      platform: FakePlatform(
+        environment: <String, String>{'FLUTTER_ROOT': _kFlutterRoot},
+        operatingSystem: 'macos',
+      ),
+      log: log.add,
+    );
 
-        comparator = await FlutterLocalFileComparator.fromDefaultComparator(
-          platform,
-          goldens: fakeSkiaClient,
-          baseDirectory: fakeDirectory,
-        );
-        expect(comparator.runtimeType, FlutterSkippingFileComparator);
-        // reset property or it will carry on to other tests
-        fakeSkiaClient.getExpectationForTestThrowable = null;
-      });
-    });
+    const String hash = '55109a4bed52acc780530f7a9aeff6c0';
+    fakeSkiaClient.expectationForTestValues['flutter.golden_test.1'] = hash;
+    fakeSkiaClient.imageBytesValues[hash] =_kTestPngBytes;
+    fakeSkiaClient.cleanTestNameValues['library.flutter.golden_test.1.png'] = 'flutter.golden_test.1';
+    expect(
+      await comparator.compare(
+        Uint8List.fromList(_kTestPngBytes),
+        Uri.parse('flutter.golden_test.1.png'),
+      ),
+      isTrue,
+    );
+    expect(log, isEmpty);
+  });
+
+  test('FlutterGoldenFileComparator - Local - skips when network connection is unavailable', () async {
+    final FileSystem fs = createFakeFileSystem();
+    final FakeProcessManager process = FakeProcessManager()
+      ..fallbackProcessResult = io.ProcessResult(123, 1, 'test resulted in a 502: 502 Bad Gateway\n', '');
+    final List<String> log = <String>[];
+    final FlutterGoldenFileComparator comparator = await FlutterLocalFileComparator.fromLocalFileComparator(
+      localFileComparator: LocalFileComparator(Uri.parse('/test'), pathStyle: path.Style.posix),
+      platform: FakePlatform(
+        environment: <String, String>{
+          'FLUTTER_ROOT': _kFlutterRoot,
+        },
+        operatingSystem: 'macos',
+      ),
+      fs: fs,
+      process: process,
+      httpClient: ThrowingHttpClient(),
+      log: log.add,
+    );
+    expect(
+      await comparator.compare(
+        Uint8List.fromList(_kTestPngBytes),
+        Uri.parse('flutter.golden_test.1.png'),
+      ),
+      isTrue,
+    );
+    expect(log, <String>[
+      'Auto-passing "pkg.flutter.golden_test.1.png" test, ignoring network error when contacting Skia.'
+    ]);
   });
 }
 
@@ -1207,28 +1027,27 @@ class RunInvocation {
 }
 
 class FakeProcessManager extends Fake implements ProcessManager {
-  Map<RunInvocation, ProcessResult> processResults = <RunInvocation, ProcessResult>{};
+  Map<RunInvocation, io.ProcessResult> processResults = <RunInvocation, io.ProcessResult>{};
 
   /// Used if [processResults] does not contain a matching invocation.
-  ProcessResult? fallbackProcessResult;
+  io.ProcessResult? fallbackProcessResult;
 
   final List<String?> workingDirectories = <String?>[];
 
   @override
-  Future<ProcessResult> run(
+  Future<io.ProcessResult> run(
     List<Object> command, {
     String? workingDirectory,
     Map<String, String>? environment,
     bool includeParentEnvironment = true,
     bool runInShell = false,
-    Encoding? stdoutEncoding = systemEncoding,
-    Encoding? stderrEncoding = systemEncoding,
+    Encoding? stdoutEncoding,
+    Encoding? stderrEncoding,
   }) async {
     workingDirectories.add(workingDirectory);
-    final ProcessResult? result = processResults[RunInvocation(command.cast<String>(), workingDirectory)];
+    final io.ProcessResult? result = processResults[RunInvocation(command.cast<String>(), workingDirectory)];
     if (result == null && fallbackProcessResult == null) {
-      printOnFailure('ProcessManager.run was called with $command ($workingDirectory) unexpectedly - $processResults.');
-      fail('See above.');
+      fail('ProcessManager.run was called with $command ($workingDirectory) unexpectedly - $processResults.');
     }
     return result ?? fallbackProcessResult!;
   }
@@ -1238,8 +1057,10 @@ class FakeProcessManager extends Fake implements ProcessManager {
 class FakeSkiaGoldClient extends Fake implements SkiaGoldClient {
   Map<String, String> expectationForTestValues = <String, String>{};
   Exception? getExpectationForTestThrowable;
+
   @override
   Future<String> getExpectationForTest(String testName) async {
+    await null; // force this to be async
     if (getExpectationForTestThrowable != null) {
       throw getExpectationForTestThrowable!;
     }
@@ -1247,30 +1068,51 @@ class FakeSkiaGoldClient extends Fake implements SkiaGoldClient {
   }
 
   @override
-  Future<void> auth() async {}
+  Future<void> auth() async {
+    await null; // force this to be async
+  }
 
   final List<String> testNames = <String>[];
 
   int initCalls = 0;
+
   @override
-  Future<void> imgtestInit() async => initCalls += 1;
+  Future<void> imgtestInit() async {
+    await null; // force this to be async
+    initCalls += 1;
+  }
+
   @override
   Future<bool> imgtestAdd(String testName, File goldenFile) async {
+    await null; // force this to be async
     testNames.add(testName);
     return true;
   }
 
   int tryInitCalls = 0;
+
   @override
-  Future<void> tryjobInit() async => tryInitCalls += 1;
+  Future<void> tryjobInit() async {
+    await null; // force this to be async
+    tryInitCalls += 1;
+  }
+
   @override
-  Future<bool> tryjobAdd(String testName, File goldenFile) async => true;
+  Future<bool> tryjobAdd(String testName, File goldenFile) async {
+    await null; // force this to be async
+    return true;
+  }
 
   Map<String, List<int>> imageBytesValues = <String, List<int>>{};
+
   @override
-  Future<List<int>> getImageBytes(String imageHash) async => imageBytesValues[imageHash]!;
+  Future<List<int>> getImageBytes(String imageHash) async {
+    await null; // force this to be async
+    return imageBytesValues[imageHash]!;
+  }
 
   Map<String, String> cleanTestNameValues = <String, String>{};
+
   @override
   String cleanTestName(String fileName) => cleanTestNameValues[fileName] ?? '';
 }
@@ -1280,36 +1122,34 @@ class FakeLocalFileComparator extends Fake implements LocalFileComparator {
   late Uri basedir;
 }
 
-class FakeDirectory extends Fake implements Directory {
-  late bool existsSyncValue;
-  @override
-  bool existsSync() => existsSyncValue;
-
+class ThrowingHttpClient extends Fake implements io.HttpClient {
   @override
-  late Uri uri;
+  Future<io.HttpClientRequest> getUrl(Uri url) async {
+    throw const io.SocketException('test error');
+  }
 }
 
-class FakeHttpClient extends Fake implements HttpClient {
+class FakeHttpClient extends Fake implements io.HttpClient {
   late Uri lastUri;
   late FakeHttpClientRequest request;
 
   @override
-  Future<HttpClientRequest> getUrl(Uri url) async {
+  Future<io.HttpClientRequest> getUrl(Uri url) async {
     lastUri = url;
     return request;
   }
 }
 
-class FakeHttpClientRequest extends Fake implements HttpClientRequest {
+class FakeHttpClientRequest extends Fake implements io.HttpClientRequest {
   late FakeHttpImageResponse response;
 
   @override
-  Future<HttpClientResponse> close() async {
+  Future<io.HttpClientResponse> close() async {
     return response;
   }
 }
 
-class FakeHttpImageResponse extends Fake implements HttpClientResponse {
+class FakeHttpImageResponse extends Fake implements io.HttpClientResponse {
   FakeHttpImageResponse(this.response);
 
   final List<List<int>> response;
@@ -1319,3 +1159,22 @@ class FakeHttpImageResponse extends Fake implements HttpClientResponse {
     response.forEach(action);
   }
 }
+
+class LoggingProcessManager extends Fake implements ProcessManager {
+  LoggingProcessManager(this.log);
+
+  final List<String> log;
+
+  @override
+  Future<io.ProcessResult> run(List<Object> command, {
+    Map<String, String>? environment,
+    bool includeParentEnvironment = true,
+    bool runInShell = false,
+    Encoding? stderrEncoding,
+    Encoding? stdoutEncoding,
+    String? workingDirectory,
+  }) async {
+    log.add(command.join(' '));
+    return io.ProcessResult(0, 0, '200', '');
+  }
+}

packages/flutter_goldens/test/skia_client_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io' show HttpClient, ProcessResult;
+
+import 'package:file/file.dart';
+import 'package:file/memory.dart';
+import 'package:flutter_goldens/skia_client.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:platform/platform.dart';
+import 'package:process/process.dart';
+
+void main() {
+  test('502 retry', () async {
+    final List<String> log = <String>[];
+    await runZoned(
+      zoneSpecification: ZoneSpecification(
+        print: (Zone self, ZoneDelegate parent, Zone zone, String line) {
+          fail('unexpected print: "$line"');
+        },
+        createTimer: (Zone self, ZoneDelegate parent, Zone zone, Duration duration, void Function() f) {
+          log.add('CREATED TIMER: $duration');
+          return parent.createTimer(zone, Duration.zero, f);
+        },
+      ),
+      () async {
+        final FileSystem fs;
+        final SkiaGoldClient skiaClient = SkiaGoldClient(
+          fs: fs = MemoryFileSystem(),
+          process: FakeProcessManager(log),
+          platform: FakePlatform(
+            environment: const <String, String>{
+              'GOLDCTL': 'goldctl',
+            },
+          ),
+          httpClient: FakeHttpClient(),
+          log: log.add,
+          fs.directory('/'),
+        );
+        log.add('START'); // ignore: avoid_print
+        await skiaClient.tryjobAdd('test', fs.file('golden'));
+        log.add('END'); // ignore: avoid_print
+        expect(log, <String>[
+          'START',
+          'EXEC: goldctl imgtest add --work-dir /temp --test-name t --png-file golden',
+          'Transient failure (exit code 1) from Skia Gold.',
+          '',
+          'stdout from gold:',
+          '  test resulted in a 502: 502 Bad Gateway',
+          '  ',
+          '',
+          'Retrying in 5 seconds.',
+          'CREATED TIMER: 0:00:05.000000',
+          'EXEC: goldctl imgtest add --work-dir /temp --test-name t --png-file golden',
+          'END',
+        ]);
+      },
+    );
+  });
+}
+
+class FakeProcessManager extends Fake implements ProcessManager {
+  FakeProcessManager(this.log);
+
+  final List<String> log;
+  int _index = 0;
+
+  @override
+  Future<ProcessResult> run(List<Object> command, {
+    Map<String, String>? environment,
+    bool includeParentEnvironment = true,
+    bool runInShell = false,
+    Encoding? stderrEncoding,
+    Encoding? stdoutEncoding,
+    String? workingDirectory,
+  }) async {
+    log.add('EXEC: ${command.join(' ')}');
+    _index += 1;
+    switch (_index) {
+      case 1: return ProcessResult(0, 1, 'test resulted in a 502: 502 Bad Gateway\n', '');
+      case 2: return ProcessResult(0, 0, '200', '');
+      default: throw StateError('unexpected call to run');
+    }
+  }
+}
+
+class FakeHttpClient extends Fake implements HttpClient { }

packages/flutter_goldens_client/pubspec.yaml

-name: flutter_goldens_client
-
-environment:
-  sdk: '>=3.2.0-0 <4.0.0'
-
-dependencies:
-  # To update these, use "flutter update-packages --force-upgrade".
-  crypto: 3.0.3
-  file: 7.0.0
-  platform: 3.1.3
-  process: 5.0.1
-
-  collection: 1.18.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
-  meta: 1.11.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
-  path: 1.9.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
-  typed_data: 1.3.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
-
-dartdoc:
-  # Exclude this package from the hosted API docs.
-  nodoc: true
-
-# PUBSPEC CHECKSUM: 652c