[tools] Switch to flutter test (#4348)

For non-web platforms, `flutter drive` is deprecated. This switches those platforms from `flutter drive` to `flutter test`. This makes the logic to check for test driver files web-specific, since `flutter test` doesn't require a driver.

Removes support for the legacy test-in-test_driver-directory structure, which is no longer used anywhere in the repository.

Also includes a minor drive-by fix to the way we do process output, noticed while manually testing. Instead of adding all stdout, and only then adding all stderr, this adds both then waits for both, which should allow interleaving of stdout and stderr in the terminal.

Fixes https://github.com/flutter/flutter/issues/105634

script/tool/lib/src/drive_examples_command.dart

@@ -17,7 +17,7 @@ import 'common/repository_package.dart';
 const int _exitNoPlatformFlags = 2;
 const int _exitNoAvailableDevice = 3;
 
-/// A command to run the example applications for packages via Flutter driver.
+/// A command to run the integration tests for a package's example applications.
 class DriveExamplesCommand extends PackageLoopingCommand {
   /// Creates an instance of the drive command.
   DriveExamplesCommand(
@@ -50,11 +50,9 @@ class DriveExamplesCommand extends PackageLoopingCommand {
   final String name = 'drive-examples';
 
   @override
-  final String description = 'Runs driver tests for package example apps.\n\n'
-      'For each *_test.dart in test_driver/ it drives an application with '
-      'either the corresponding test in test_driver (for example, '
-      'test_driver/app_test.dart would match test_driver/app.dart), or the '
-      '*_test.dart files in integration_test/.\n\n'
+  final String description = 'Runs Dart integration tests for example apps.\n\n'
+      "This runs all tests in each example's integration_test directory, "
+      'via "flutter test" on most platforms, and "flutter drive" on web.\n\n'
       'This command requires "flutter" to be in your path.';
 
   Map<String, List<String>> _targetDeviceFlags = const <String, List<String>>{};
@@ -164,53 +162,53 @@ class DriveExamplesCommand extends PackageLoopingCommand {
             'Skipping $exampleName; does not support any requested platforms.');
         continue;
       }
+
       ++supportedExamplesFound;
 
-      final List<File> drivers = await _getDrivers(example);
-      if (drivers.isEmpty) {
-        print('No driver tests found for $exampleName');
+      final List<File> testTargets = await _getIntegrationTests(example);
+      if (testTargets.isEmpty) {
+        print('No integration_test/*.dart files found for $exampleName.');
         continue;
       }
 
-      for (final File driver in drivers) {
-        final List<File> testTargets = <File>[];
+      // Check files for known problematic patterns.
+      testTargets
+          .where((File file) => !_validateIntegrationTest(file))
+          .forEach((File file) {
+        // Report the issue, but continue with the test as the validation
+        // errors don't prevent running.
+        errors.add('${file.basename} failed validation');
+      });
 
-        // Try to find a matching app to drive without the _test.dart
-        // TODO(stuartmorgan): Migrate all remaining uses of this legacy
-        // approach (currently only video_player) and remove support for it:
-        // https://github.com/flutter/flutter/issues/85224.
-        final File? legacyTestFile = _getLegacyTestFileForTestDriver(driver);
-        if (legacyTestFile != null) {
-          testTargets.add(legacyTestFile);
-        } else {
-          for (final File testFile in await _getIntegrationTests(example)) {
-            // Check files for known problematic patterns.
-            final bool passesValidation = _validateIntegrationTest(testFile);
-            if (!passesValidation) {
-              // Report the issue, but continue with the test as the validation
-              // errors don't prevent running.
-              errors.add('${testFile.basename} failed validation');
-            }
-            testTargets.add(testFile);
-          }
-        }
+      // `flutter test` doesn't yet support web integration tests, so fall back
+      // to `flutter drive`.
+      final bool useFlutterDrive = getBoolArg(platformWeb);
 
-        if (testTargets.isEmpty) {
-          final String driverRelativePath =
-              getRelativePosixPath(driver, from: package.directory);
-          printError(
-              'Found $driverRelativePath, but no integration_test/*_test.dart files.');
-          errors.add('No test files for $driverRelativePath');
+      final List<File> drivers;
+      if (useFlutterDrive) {
+        drivers = await _getDrivers(example);
+        if (drivers.isEmpty) {
+          print('No driver found for $exampleName');
           continue;
         }
+      } else {
+        drivers = <File>[];
+      }
 
-        testsRan = true;
-        final List<File> failingTargets = await _driveTests(
-            example, driver, testTargets,
-            deviceFlags: deviceFlags);
-        for (final File failingTarget in failingTargets) {
-          errors.add(
-              getRelativePosixPath(failingTarget, from: package.directory));
+      testsRan = true;
+      if (useFlutterDrive) {
+        for (final File driver in drivers) {
+          final List<File> failingTargets = await _driveTests(
+              example, driver, testTargets,
+              deviceFlags: deviceFlags);
+          for (final File failingTarget in failingTargets) {
+            errors.add(
+                getRelativePosixPath(failingTarget, from: package.directory));
+          }
+        }
+      } else {
+        if (!await _runTests(example, deviceFlags: deviceFlags)) {
+          errors.add('Integration tests failed.');
         }
       }
     }
@@ -224,7 +222,7 @@ class DriveExamplesCommand extends PackageLoopingCommand {
       } else {
         return PackageResult.skip(supportedExamplesFound == 0
             ? 'No example supports requested platform(s).'
-            : 'No example is configured for driver tests.');
+            : 'No example is configured for integration tests.');
       }
     }
     return errors.isEmpty
@@ -295,16 +293,6 @@ class DriveExamplesCommand extends PackageLoopingCommand {
     return drivers;
   }
 
-  File? _getLegacyTestFileForTestDriver(File testDriver) {
-    final String testName = testDriver.basename.replaceAll(
-      RegExp(r'_test.dart$'),
-      '.dart',
-    );
-    final File testFile = testDriver.parent.childFile(testName);
-
-    return testFile.existsSync() ? testFile : null;
-  }
-
   Future<List<File>> _getIntegrationTests(RepositoryPackage example) async {
     final List<File> tests = <File>[];
     final Directory integrationTestDir =
@@ -378,4 +366,31 @@ class DriveExamplesCommand extends PackageLoopingCommand {
     }
     return failures;
   }
+
+  /// Uses `flutter test integration_test` to run [example], returning the
+  /// success of the test run.
+  ///
+  /// [deviceFlags] should contain the flags to run the test on a specific
+  /// target device (plus any supporting device-specific flags). E.g.:
+  ///   - `['-d', 'macos']` for driving for macOS.
+  ///   - `['-d', 'web-server', '--web-port=<port>', '--browser-name=<browser>]`
+  ///     for web
+  Future<bool> _runTests(
+    RepositoryPackage example, {
+    required List<String> deviceFlags,
+  }) async {
+    final String enableExperiment = getStringArg(kEnableExperiment);
+
+    final int exitCode = await processRunner.runAndStream(
+        flutterCommand,
+        <String>[
+          'test',
+          ...deviceFlags,
+          if (enableExperiment.isNotEmpty)
+            '--enable-experiment=$enableExperiment',
+          'integration_test',
+        ],
+        workingDir: example.directory);
+    return exitCode == 0;
+  }
 }