[file_selector] Remove use of Pigeon's Dart test generator (#10315)

Updates `file_selector_ios`, `_macos`, and `_windows` tests to use the same structure as `file_selector_linux` already uses:
- Removes the use of Pigeon's Dart test generator in favor of DI'ing an implementation of the actual generated Dart API.
- Removes the use of `mockito` in favor of a fake, since the fake is extremely simple to maintain and it makes the tests simpler.

Part of flutter/flutter#159886

## Pre-Review Checklist

[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.

Author: stuartmorgan-g

packages/file_selector/file_selector_ios/lib/file_selector_ios.dart

@@ -3,12 +3,17 @@
 // found in the LICENSE file.
 
 import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';
+import 'package:flutter/foundation.dart' show visibleForTesting;
 
 import 'src/messages.g.dart';
 
 /// An implementation of [FileSelectorPlatform] for iOS.
 class FileSelectorIOS extends FileSelectorPlatform {
-  final FileSelectorApi _hostApi = FileSelectorApi();
+  /// Creates a new plugin implementation instance.
+  FileSelectorIOS({@visibleForTesting FileSelectorApi? api})
+    : _hostApi = api ?? FileSelectorApi();
+
+  final FileSelectorApi _hostApi;
 
   /// Registers the iOS implementation.
   static void registerWith() {

packages/file_selector/file_selector_ios/pigeons/messages.dart

@@ -7,7 +7,6 @@ import 'package:pigeon/pigeon.dart';
 @ConfigurePigeon(
   PigeonOptions(
     dartOut: 'lib/src/messages.g.dart',
-    dartTestOut: 'test/test_api.g.dart',
     swiftOut:
         'ios/file_selector_ios/Sources/file_selector_ios/messages.g.swift',
     copyrightHeader: 'pigeons/copyright.txt',
@@ -22,7 +21,7 @@ class FileSelectorConfig {
   bool allowMultiSelection;
 }
 
-@HostApi(dartHostTestHandler: 'TestFileSelectorApi')
+@HostApi()
 abstract class FileSelectorApi {
   @async
   @ObjCSelector('openFileSelectorWithConfig:')

packages/file_selector/file_selector_ios/pubspec.yaml

@@ -22,10 +22,8 @@ dependencies:
     sdk: flutter
 
 dev_dependencies:
-  build_runner: ^2.3.0
   flutter_test:
     sdk: flutter
-  mockito: ^5.4.4
   pigeon: ^25.5.0
 
 topics:

packages/file_selector/file_selector_ios/test/file_selector_ios_test.dart

@@ -6,23 +6,18 @@ import 'package:file_selector_ios/file_selector_ios.dart';
 import 'package:file_selector_ios/src/messages.g.dart';
 import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:mockito/annotations.dart';
-import 'package:mockito/mockito.dart';
 
-import 'file_selector_ios_test.mocks.dart';
-import 'test_api.g.dart';
-
-@GenerateMocks(<Type>[TestFileSelectorApi])
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
-  final FileSelectorIOS plugin = FileSelectorIOS();
-  late MockTestFileSelectorApi mockApi;
+  late FakeFileSelectorApi api;
+  late FileSelectorIOS plugin;
 
   setUp(() {
-    mockApi = MockTestFileSelectorApi();
-    TestFileSelectorApi.setUp(mockApi);
+    api = FakeFileSelectorApi();
+    plugin = FileSelectorIOS(api: api);
   });
 
   test('registered instance', () {
@@ -32,7 +27,7 @@ void main() {
 
   group('openFile', () {
     setUp(() {
-      when(mockApi.openFile(any)).thenAnswer((_) async => <String>['foo']);
+      api.result = <String>['foo'];
     });
 
     test('passes the accepted type groups correctly', () async {
@@ -53,16 +48,15 @@ void main() {
 
       await plugin.openFile(acceptedTypeGroups: <XTypeGroup>[group, groupTwo]);
 
-      final VerificationResult result = verify(mockApi.openFile(captureAny));
-      final FileSelectorConfig config =
-          result.captured[0] as FileSelectorConfig;
-
       // iOS only accepts uniformTypeIdentifiers.
       expect(
-        listEquals(config.utis, <String>['public.text', 'public.image']),
+        listEquals(api.passedConfig?.utis, <String>[
+          'public.text',
+          'public.image',
+        ]),
         isTrue,
       );
-      expect(config.allowMultiSelection, isFalse);
+      expect(api.passedConfig?.allowMultiSelection, isFalse);
     });
     test('throws for a type group that does not support iOS', () async {
       const XTypeGroup group = XTypeGroup(
@@ -78,10 +72,10 @@ void main() {
 
     test('correctly handles no type groups', () async {
       await expectLater(plugin.openFile(), completes);
-      final VerificationResult result = verify(mockApi.openFile(captureAny));
-      final FileSelectorConfig config =
-          result.captured[0] as FileSelectorConfig;
-      expect(listEquals(config.utis, <String>['public.data']), isTrue);
+      expect(
+        listEquals(api.passedConfig?.utis, <String>['public.data']),
+        isTrue,
+      );
     });
 
     test('correctly handles a wildcard group', () async {
@@ -91,16 +85,16 @@ void main() {
         plugin.openFile(acceptedTypeGroups: <XTypeGroup>[group]),
         completes,
       );
-      final VerificationResult result = verify(mockApi.openFile(captureAny));
-      final FileSelectorConfig config =
-          result.captured[0] as FileSelectorConfig;
-      expect(listEquals(config.utis, <String>['public.data']), isTrue);
+      expect(
+        listEquals(api.passedConfig?.utis, <String>['public.data']),
+        isTrue,
+      );
     });
   });
 
   group('openFiles', () {
     setUp(() {
-      when(mockApi.openFile(any)).thenAnswer((_) async => <String>['foo']);
+      api.result = <String>['foo'];
     });
 
     test('passes the accepted type groups correctly', () async {
@@ -121,16 +115,14 @@ void main() {
 
       await plugin.openFiles(acceptedTypeGroups: <XTypeGroup>[group, groupTwo]);
 
-      final VerificationResult result = verify(mockApi.openFile(captureAny));
-      final FileSelectorConfig config =
-          result.captured[0] as FileSelectorConfig;
-
-      // iOS only accepts uniformTypeIdentifiers.
       expect(
-        listEquals(config.utis, <String>['public.text', 'public.image']),
+        listEquals(api.passedConfig?.utis, <String>[
+          'public.text',
+          'public.image',
+        ]),
         isTrue,
       );
-      expect(config.allowMultiSelection, isTrue);
+      expect(api.passedConfig?.allowMultiSelection, isTrue);
     });
 
     test('throws for a type group that does not support iOS', () async {
@@ -147,10 +139,10 @@ void main() {
 
     test('correctly handles no type groups', () async {
       await expectLater(plugin.openFiles(), completes);
-      final VerificationResult result = verify(mockApi.openFile(captureAny));
-      final FileSelectorConfig config =
-          result.captured[0] as FileSelectorConfig;
-      expect(listEquals(config.utis, <String>['public.data']), isTrue);
+      expect(
+        listEquals(api.passedConfig?.utis, <String>['public.data']),
+        isTrue,
+      );
     });
 
     test('correctly handles a wildcard group', () async {
@@ -160,10 +152,30 @@ void main() {
         plugin.openFiles(acceptedTypeGroups: <XTypeGroup>[group]),
         completes,
       );
-      final VerificationResult result = verify(mockApi.openFile(captureAny));
-      final FileSelectorConfig config =
-          result.captured[0] as FileSelectorConfig;
-      expect(listEquals(config.utis, <String>['public.data']), isTrue);
+      expect(
+        listEquals(api.passedConfig?.utis, <String>['public.data']),
+        isTrue,
+      );
     });
   });
 }
+
+/// Fake implementation that stores arguments and provides a canned response.
+class FakeFileSelectorApi implements FileSelectorApi {
+  List<String> result = <String>[];
+  FileSelectorConfig? passedConfig;
+
+  @override
+  Future<List<String>> openFile(FileSelectorConfig config) async {
+    passedConfig = config;
+    return result;
+  }
+
+  @override
+  // ignore: non_constant_identifier_names
+  BinaryMessenger? get pigeonVar_binaryMessenger => null;
+
+  @override
+  // ignore: non_constant_identifier_names
+  String get pigeonVar_messageChannelSuffix => '';
+}

packages/file_selector/file_selector_ios/test/file_selector_ios_test.mocks.dart

@@ -52,7 +52,7 @@ class PlatformFileChooserOptions {
   final bool? selectMultiple;
 }
 
-@HostApi(dartHostTestHandler: 'TestFileSelectorApi')
+@HostApi()
 abstract class FileSelectorApi {
   /// Shows an file chooser with the given [type] and [options], returning the
   /// list of selected paths.

packages/file_selector/file_selector_ios/test/test_api.g.dart

@@ -3,12 +3,17 @@
 // found in the LICENSE file.
 
 import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';
+import 'package:flutter/foundation.dart' show visibleForTesting;
 
 import 'src/messages.g.dart';
 
 /// An implementation of [FileSelectorPlatform] for macOS.
 class FileSelectorMacOS extends FileSelectorPlatform {
-  final FileSelectorApi _hostApi = FileSelectorApi();
+  /// Creates a new plugin implementation instance.
+  FileSelectorMacOS({@visibleForTesting FileSelectorApi? api})
+    : _hostApi = api ?? FileSelectorApi();
+
+  final FileSelectorApi _hostApi;
 
   /// Registers the macOS implementation.
   static void registerWith() {