Add a test for the isAvailableForEnvironment logic (#142251)

This is part 3 of a broken down version of the #140101 refactor.

There's some TODOs showing where I think we should change the behaviour, but in this PR the behaviour is unchanged.
A future PR will remove the tests that are redundant with these tests, but I wanted to make sure we had both sets in the codebase at the same time first.
This PR includes a change to the golden control test so that we can verify that these specific values do work on main. It would be extremely surprising if not, but in the interests of rigour...

packages/flutter/test/widgets/basic_test.dart

@@ -752,7 +752,7 @@ void main() {
     // golden file can be approved at any time.
     await tester.pumpWidget(RepaintBoundary(
       child: Container(
-        color: const Color(0xABCDABCD),
+        color: const Color(0x20240125),
       ),
     ));
 

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.isAvailableForEnvironment(platform)) {
+    return _Comparator.post;
+  }
+  if (FlutterPreSubmitFileComparator.isAvailableForEnvironment(platform)) {
+    return _Comparator.pre;
+  }
+  if (FlutterSkippingFileComparator.isAvailableForEnvironment(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.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasLuci: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasLuci: true, hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasFlutterRoot: true, hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true, hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be 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.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(hasCirrus: true, hasGold: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be 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.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasLuci: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasLuci: true, hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasCirrus: true), _Comparator.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be 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.local); // TODO(ianh): this should be skip
+    expect(_testRecommendations(os: 'linux', hasCirrus: true, hasGold: true, hasFlutterRoot: true, hasTryJob: true), _Comparator.local); // TODO(ianh): this should be skip
+  });
+}