Add sharding options to test command line (#76382)

packages/flutter_tools/lib/src/commands/test.dart

@@ -140,6 +140,16 @@ class TestCommand extends FlutterCommand {
               'which indicates that a seed should be selected randomly. '
               'By default, tests run in the order they are declared.',
       )
+      ..addOption('total-shards',
+        help: 'Tests can be sharded with the "--total-shards" and "--shard-index" '
+              'arguments, allowing you to split up your test suites and run '
+              'them separately.'
+      )
+      ..addOption('shard-index',
+          help: 'Tests can be sharded with the "--total-shards" and "--shard-index" '
+              'arguments, allowing you to split up your test suites and run '
+              'them separately.'
+      )
       ..addFlag('enable-vmservice',
         defaultsTo: false,
         hide: !verboseHelp,
@@ -265,6 +275,27 @@ class TestCommand extends FlutterCommand {
       ];
     }
 
+    final int shardIndex = int.tryParse(stringArg('shard-index') ?? '');
+    if (shardIndex != null && (shardIndex < 0 || !shardIndex.isFinite)) {
+      throwToolExit(
+          'Could not parse --shard-index=$shardIndex argument. It must be an integer greater than -1.');
+    }
+
+    final int totalShards = int.tryParse(stringArg('total-shards') ?? '');
+    if (totalShards != null && (totalShards <= 0 || !totalShards.isFinite)) {
+      throwToolExit(
+          'Could not parse --total-shards=$totalShards argument. It must be an integer greater than zero.');
+    }
+
+    if (totalShards != null && shardIndex == null) {
+      throwToolExit(
+          'If you set --total-shards you need to also set --shard-index.');
+    }
+    if (shardIndex != null && totalShards == null) {
+      throwToolExit(
+          'If you set --shard-index you need to also set --total-shards.');
+    }
+
     final bool machine = boolArg('machine');
     CoverageCollector collector;
     if (boolArg('coverage') || boolArg('merge-coverage')) {
@@ -314,6 +345,8 @@ class TestCommand extends FlutterCommand {
       reporter: stringArg('reporter'),
       timeout: stringArg('timeout'),
       runSkipped: boolArg('run-skipped'),
+      shardIndex: shardIndex,
+      totalShards: totalShards,
     );
 
     if (collector != null) {

packages/flutter_tools/lib/src/test/runner.dart

@@ -51,6 +51,8 @@ abstract class FlutterTestRunner {
     String reporter,
     String timeout,
     bool runSkipped = false,
+    int shardIndex,
+    int totalShards,
   });
 }
 
@@ -83,6 +85,8 @@ class _FlutterTestRunnerImpl implements FlutterTestRunner {
     String reporter,
     String timeout,
     bool runSkipped = false,
+    int shardIndex,
+    int totalShards,
   }) async {
     // Configure package:test to use the Flutter engine for child processes.
     final String shellPath = globals.artifacts.getArtifactPath(Artifact.flutterTester);
@@ -112,6 +116,10 @@ class _FlutterTestRunnerImpl implements FlutterTestRunner {
         ...<String>['--exclude-tags', excludeTags],
       if (runSkipped)
         '--run-skipped',
+      if (totalShards != null)
+        '--total-shards=$totalShards',
+      if (shardIndex != null)
+        '--shard-index=$shardIndex',
     ];
     if (web) {
       final String tempBuildDir = globals.fs.systemTempDirectory

packages/flutter_tools/test/commands.shard/hermetic/test_test.dart

@@ -59,6 +59,52 @@ void main() {
     Cache: () => FakeCache(),
   });
 
+  group('shard-index and total-shards', () {
+    testUsingContext('with the params they are Piped to package:test',
+        () async {
+      final FakePackageTest fakePackageTest = FakePackageTest();
+
+      final TestCommand testCommand = TestCommand(testWrapper: fakePackageTest);
+      final CommandRunner<void> commandRunner =
+          createTestCommandRunner(testCommand);
+
+      await commandRunner.run(const <String>[
+        'test',
+        '--total-shards=1',
+        '--shard-index=2',
+        '--no-pub',
+      ]);
+
+      expect(fakePackageTest.lastArgs, contains('--total-shards=1'));
+      expect(fakePackageTest.lastArgs, contains('--shard-index=2'));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fs,
+      ProcessManager: () => FakeProcessManager.any(),
+      Cache: () => FakeCache(),
+    });
+
+    testUsingContext('without the params they not Piped to package:test',
+        () async {
+      final FakePackageTest fakePackageTest = FakePackageTest();
+
+      final TestCommand testCommand = TestCommand(testWrapper: fakePackageTest);
+      final CommandRunner<void> commandRunner =
+          createTestCommandRunner(testCommand);
+
+      await commandRunner.run(const <String>[
+        'test',
+        '--no-pub',
+      ]);
+
+      expect(fakePackageTest.lastArgs, isNot(contains('--total-shards')));
+      expect(fakePackageTest.lastArgs, isNot(contains('--shard-index')));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fs,
+      ProcessManager: () => FakeProcessManager.any(),
+      Cache: () => FakeCache(),
+    });
+  });
+
   testUsingContext('Supports coverage and machine', () async {
     final FakePackageTest fakePackageTest = FakePackageTest();
 
@@ -216,6 +262,8 @@ class FakeFlutterTestRunner implements FlutterTestRunner {
     String reporter,
     String timeout,
     bool runSkipped = false,
+    int shardIndex,
+    int totalShards,
   }) async {
     lastEnableObservatoryValue = enableObservatory;
     return exitCode;