Remove the warning about the Integration Test plugin (#79520)

dev/automated_tests/integration_test/trivial_widget_expectation.txt

-<<skip until matching line>>
 [0-9]+:[0-9]+ [+]1: All tests passed!

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

@@ -401,6 +401,10 @@ class TestCommand extends FlutterCommand with DeviceBasedDevelopmentArtifacts {
     if (_isIntegrationTest) {
       integrationTestDevice = await findTargetDevice();
 
+      // Disable reporting of test results to native test frameworks. This isn't
+      // needed as the Flutter Tool will be responsible for reporting results.
+      buildInfo.dartDefines.add('INTEGRATION_TEST_SHOULD_REPORT_RESULTS_TO_NATIVE=false');
+
       if (integrationTestDevice == null) {
         throwToolExit(
           'No devices are connected. '

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

@@ -582,6 +582,30 @@ dev_dependencies:
       FakeDevice('ephemeral', 'ephemeral', ephemeral: true, isSupported: true, type: PlatformType.web),
     ]),
   });
+
+  testUsingContext('Integration tests set the correct dart-defines', () async {
+    final FakeFlutterTestRunner testRunner = FakeFlutterTestRunner(0);
+
+    final TestCommand testCommand = TestCommand(testRunner: testRunner);
+    final CommandRunner<void> commandRunner = createTestCommandRunner(testCommand);
+
+    await commandRunner.run(const <String>[
+      'test',
+      '--no-pub',
+      'integration_test',
+    ]);
+
+    expect(
+      testRunner.lastDebuggingOptionsValue.buildInfo.dartDefines,
+      contains('INTEGRATION_TEST_SHOULD_REPORT_RESULTS_TO_NATIVE=false'),
+    );
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fs,
+    ProcessManager: () => FakeProcessManager.any(),
+    DeviceManager: () => _FakeDeviceManager(<Device>[
+      FakeDevice('ephemeral', 'ephemeral', ephemeral: true, isSupported: true, type: PlatformType.android),
+    ]),
+  });
 }
 
 class FakeFlutterTestRunner implements FlutterTestRunner {
@@ -589,6 +613,7 @@ class FakeFlutterTestRunner implements FlutterTestRunner {
 
   int exitCode;
   bool lastEnableObservatoryValue;
+  DebuggingOptions lastDebuggingOptionsValue;
 
   @override
   Future<int> runTests(
@@ -626,6 +651,7 @@ class FakeFlutterTestRunner implements FlutterTestRunner {
     String integrationTestUserIdentifier,
   }) async {
     lastEnableObservatoryValue = enableObservatory;
+    lastDebuggingOptionsValue = debuggingOptions;
     return exitCode;
   }
 }

packages/integration_test/lib/integration_test.dart

@@ -20,24 +20,37 @@ import 'common.dart';
 
 const String _success = 'success';
 
+/// Whether results should be reported to the native side over the method
+/// channel.
+///
+/// This is enabled by default for use by native test frameworks like Android
+/// instrumentation or XCTest. When running with the Flutter Tool through
+/// `flutter test integration_test` though, it will be disabled as the Flutter
+/// tool will be responsible for collection of test results.
+const bool _shouldReportResultsToNative = bool.fromEnvironment(
+  'INTEGRATION_TEST_SHOULD_REPORT_RESULTS_TO_NATIVE',
+  defaultValue: true,
+);
+
 /// A subclass of [LiveTestWidgetsFlutterBinding] that reports tests results
 /// on a channel to adapt them to native instrumentation test format.
 class IntegrationTestWidgetsFlutterBinding extends LiveTestWidgetsFlutterBinding implements IntegrationTestResults {
   /// Sets up a listener to report that the tests are finished when everything is
   /// torn down.
   IntegrationTestWidgetsFlutterBinding() {
-    // TODO(jackson): Report test results as they arrive
     tearDownAll(() async {
+      if (!_allTestsPassed.isCompleted) {
+        _allTestsPassed.complete(true);
+      }
+      callbackManager.cleanup();
+
+      // TODO(jiahaog): Print the message directing users to run with
+      // `flutter test` when Web is supported.
+      if (!_shouldReportResultsToNative || kIsWeb) {
+        return;
+      }
+
       try {
-        // For web integration tests we are not using the
-        // `plugins.flutter.io/integration_test`. Mark the tests as complete
-        // before invoking the channel.
-        if (kIsWeb) {
-          if (!_allTestsPassed.isCompleted) {
-            _allTestsPassed.complete(true);
-          }
-        }
-        callbackManager.cleanup();
         await _channel.invokeMethod<void>(
           'allTestsFinished',
           <String, dynamic>{
@@ -50,15 +63,22 @@ class IntegrationTestWidgetsFlutterBinding extends LiveTestWidgetsFlutterBinding
           },
         );
       } on MissingPluginException {
-        print('Warning: integration_test test plugin was not detected.');
-      }
-      if (!_allTestsPassed.isCompleted) {
-        _allTestsPassed.complete(true);
+        print(r'''
+Warning: integration_test plugin was not detected.
+
+If you're running the tests with `flutter drive`, please make sure your tests
+are in the `integration_test/` directory of your package and use
+`flutter test $path_to_test` to run it instead.
+
+If you're running the tests with Android instrumentation or XCTest, this means
+that you are not capturing test results properly! See the following link for
+how to set up the integration_test plugin:
+
+https://flutter.dev/docs/testing/integration-tests#testing-on-firebase-test-lab
+''');
       }
     });
 
-    // TODO(jackson): Report the results individually instead of all at once
-    // See https://github.com/flutter/flutter/issues/38985
     final TestExceptionReporter oldTestExceptionReporter = reportTestException;
     reportTestException =
         (FlutterErrorDetails details, String testDescription) {