Add an integration test to plugin template example (#117062)

* Add an integration test to plugin template example

Dart unit tests don't exercise host-side plugin code at all, so the
example tests in the plugin template currently have very little
meaningful coverage. This adds an integration test to the example app
when creating a plugin, so that there's an example of how to actually
test that a complete round-trip plugin call works.

This is done as a separate template that's currently only used by the
plugin template because I don't know what a good example for a
non-plugin case would be that isn't largely just a duplicate of the
widget tests. However, the integration test pre-includes conditionals
around the parts that are plugin-specific so that it can more easily be
expanded to other use cases later (e.g., in
https://github.com/flutter/flutter/issues/68818).

Part of https://github.com/flutter/flutter/issues/82458

* Add integration test to expected dependencies of a plugin app

* Test fixes

* Make an explicit test case

dev/devicelab/bin/tasks/plugin_dependencies_test.dart

@@ -215,6 +215,10 @@ public class DummyPluginAClass {
       final List<dynamic> dependencyGraph = jsonContent['dependencyGraph'] as List<dynamic>;
       const String kExpectedPluginsDependenciesContent =
         '['
+          '{'
+            '"name":"integration_test",'
+            '"dependencies":[]'
+          '},'
           '{'
             '"name":"plugin_a",'
             '"dependencies":["plugin_b","plugin_c","plugin_d"]'

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

@@ -595,7 +595,7 @@ Your $application code is in $relativeAppMain.
     templateContext['androidPluginIdentifier'] = androidPluginIdentifier;
 
     generatedCount += await generateApp(
-      <String>['app', 'app_test_widget'],
+      <String>['app', 'app_test_widget', 'app_integration_test'],
       project.example.directory,
       templateContext,
       overwrite: overwrite,

packages/flutter_tools/templates/app/pubspec.yaml.tmpl

@@ -68,6 +68,10 @@ dependencies:
   cupertino_icons: ^1.0.2
 
 dev_dependencies:
+{{#withPlatformChannelPluginHook}}
+  integration_test:
+    sdk: flutter
+{{/withPlatformChannelPluginHook}}
   flutter_test:
     sdk: flutter
 

packages/flutter_tools/templates/app_integration_test/integration_test/plugin_integration_test.dart.tmpl

+// This is a basic Flutter integration test.
+{{#withPlatformChannelPluginHook}}
+//
+// Since integration tests run in a full Flutter application, they can interact
+// with the host side of a plugin implementation, unlike Dart unit tests.
+{{/withPlatformChannelPluginHook}}
+//
+// For more information about Flutter integration tests, please see
+// https://docs.flutter.dev/cookbook/testing/integration/introduction
+
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:integration_test/integration_test.dart';
+
+{{#withPlatformChannelPluginHook}}
+import 'package:{{pluginProjectName}}/{{pluginProjectName}}.dart';
+{{/withPlatformChannelPluginHook}}
+
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+{{#withPlatformChannelPluginHook}}
+
+  testWidgets('getPlatformVersion test', (WidgetTester tester) async {
+    final {{pluginDartClass}} plugin = {{pluginDartClass}}();
+    final String? version = await plugin.getPlatformVersion();
+    // The version string depends on the host platform running the test, so
+    // just assert that some non-empty string is returned.
+    expect(version?.isNotEmpty, true);
+  });
+{{/withPlatformChannelPluginHook}}
+}

packages/flutter_tools/templates/template_manifest.json

@@ -141,6 +141,8 @@
 
         "templates/app_test_widget/test/widget_test.dart.tmpl",
 
+        "templates/app_integration_test/integration_test/plugin_integration_test.dart.tmpl",
+
         "templates/cocoapods/Podfile-ios-objc",
         "templates/cocoapods/Podfile-ios-swift",
         "templates/cocoapods/Podfile-macos",

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

@@ -75,6 +75,7 @@ void main() {
         }
         final List<String> templatePaths = <String>[
           globals.fs.path.join('flutter', 'packages', 'flutter_tools', 'templates', 'app'),
+          globals.fs.path.join('flutter', 'packages', 'flutter_tools', 'templates', 'app_integration_test'),
           globals.fs.path.join('flutter', 'packages', 'flutter_tools', 'templates', 'app_shared'),
           globals.fs.path.join('flutter', 'packages', 'flutter_tools', 'templates', 'app_test_widget'),
           globals.fs.path.join('flutter', 'packages', 'flutter_tools', 'templates', 'cocoapods'),

packages/flutter_tools/test/commands.shard/permeable/create_test.dart

@@ -633,6 +633,27 @@ void main() {
     ),
   });
 
+  testUsingContext('plugin example app includes an integration test', () async {
+    await _createAndAnalyzeProject(
+      projectDir,
+      <String>['--template=plugin'],
+      <String>[
+        'example/integration_test/plugin_integration_test.dart',
+      ],
+    );
+    return _runFlutterTest(projectDir.childDirectory('example'));
+  }, overrides: <Type, Generator>{
+    Pub: () => Pub.test(
+      fileSystem: globals.fs,
+      logger: globals.logger,
+      processManager: globals.processManager,
+      usage: globals.flutterUsage,
+      botDetector: globals.botDetector,
+      platform: globals.platform,
+      stdio: mockStdio,
+    ),
+  });
+
   testUsingContext('kotlin/swift plugin project', () async {
     return _createProject(
       projectDir,

packages/flutter_tools/test/commands.shard/permeable/packages_test.dart

@@ -285,7 +285,8 @@ void main() {
       final PackagesCommand command = await runCommandIn(exampleProjectPath, 'get');
       final PackagesGetCommand getCommand = command.subcommands['get']! as PackagesGetCommand;
 
-      expect((await getCommand.usageValues).commandPackagesNumberPlugins, 1);
+      // A plugin example depends on the plugin itself, and integration_test.
+      expect((await getCommand.usageValues).commandPackagesNumberPlugins, 2);
     }, overrides: <Type, Generator>{
       Stdio: () => mockStdio,
       Pub: () => Pub.test(