[url_launcher] Alternative to isMock

packages/url_launcher/url_launcher/test/url_launcher_test.dart

@@ -13,7 +13,6 @@ import 'package:flutter/services.dart' show PlatformException;
 
 void main() {
   final MockUrlLauncher mock = MockUrlLauncher();
-  when(mock.isMock).thenReturn(true);
   UrlLauncherPlatform.instance = mock;
 
   test('closeWebView default behavior', () async {
@@ -208,4 +207,4 @@ void main() {
   });
 }
 
-class MockUrlLauncher extends Mock implements UrlLauncherPlatform {}
+class MockUrlLauncher extends Mock with MockPlatformInterface implements UrlLauncherPlatform {}

packages/url_launcher/url_launcher_platform_interface/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.0.4
+
+* Remove `@visibleForTesting` API `isMock`.
+* Introduces `MockPlatformInterface` and `PlatformInterface` classes.
+
 ## 1.0.3
 
 * Minor DartDoc changes and add a lint for missing DartDocs.

packages/url_launcher/url_launcher_platform_interface/lib/url_launcher_platform_interface.dart

@@ -8,42 +8,85 @@ import 'package:meta/meta.dart' show required, visibleForTesting;
 
 import 'method_channel_url_launcher.dart';
 
+/// Base class for platform interfaces.
+///
+/// Provides a static helper method for ensuring that platform interfaces are
+/// implemented using `extends` instead of `implements`.
+// TODO(amirh): Extract common platform interface logic.
+// https://github.com/flutter/flutter/issues/43368
+abstract class PlatformInterface {
+  /// Pass a private, class-specific `const Object()` as the `token`.
+  PlatformInterface({@required Object token}) : _instanceToken = token;
+
+  final Object _instanceToken;
+
+  /// Ensures that the platform instance has a token that matches the
+  /// provided token and throws [AssertionError] if not.
+  ///
+  /// This is used to ensure that implementers are using `extends` rather than
+  /// `implements`.
+  ///
+  /// Subclasses of [MockPlatformInterface] are assumed to be valid in debug
+  /// builds.
+  ///
+  /// This is implemented as a static method so that it cannot be overridden
+  /// with `noSuchMethod`.
+  static void verifyToken(PlatformInterface instance, Object token) {
+    if (identical(instance._instanceToken, MockPlatformInterface._token)) {
+      bool assertionsEnabled = false;
+      assert(() {
+        assertionsEnabled = true;
+        return true;
+      }());
+      if (!assertionsEnabled) {
+        throw AssertionError(
+            '`MockPlatformInterface` is not intended for use in release builds.');
+      }
+    }
+    if (!identical(token, instance._instanceToken)) {
+      throw AssertionError(
+          'Platform interfaces must not be implemented with `implements`');
+    }
+  }
+}
+
+/// A [PlatformInterface] mixin that can be combined with mockito's `Mock`.
+///
+/// It passes the [PlatformInterface.verifyToken] check even though it isn't
+/// using `extends`.
+///
+/// This class is intended for use in tests only.
+@visibleForTesting
+abstract class MockPlatformInterface implements PlatformInterface {
+  static const Object _token = Object();
+
+  @override
+  Object get _instanceToken => _token;
+}
+
 /// The interface that implementations of url_launcher must implement.
 ///
 /// Platform implementations should extend this class rather than implement it as `url_launcher`
 /// does not consider newly added methods to be breaking changes. Extending this class
 /// (using `extends`) ensures that the subclass will get the default implementation, while
 /// platform implementations that `implements` this interface will be broken by newly added
 /// [UrlLauncherPlatform] methods.
-abstract class UrlLauncherPlatform {
-  /// Only mock implementations should set this to true.
-  ///
-  /// Mockito mocks are implementing this class with `implements` which is forbidden for anything
-  /// other than mocks (see class docs). This property provides a backdoor for mockito mocks to
-  /// skip the verification that the class isn't implemented with `implements`.
-  @visibleForTesting
-  bool get isMock => false;
+abstract class UrlLauncherPlatform extends PlatformInterface {
+  UrlLauncherPlatform() : super(token: _token);
 
   static UrlLauncherPlatform _instance = MethodChannelUrlLauncher();
 
+  static const Object _token = Object();
+
   /// The default instance of [UrlLauncherPlatform] to use.
   ///
   /// Defaults to [MethodChannelUrlLauncher].
   static UrlLauncherPlatform get instance => _instance;
 
   /// Platform-specific plugins should set this with their own platform-specific
   /// class that extends [UrlLauncherPlatform] when they register themselves.
-  // TODO(amirh): Extract common platform interface logic.
-  // https://github.com/flutter/flutter/issues/43368
   static set instance(UrlLauncherPlatform instance) {
-    if (!instance.isMock) {
-      try {
-        instance._verifyProvidesDefaultImplementations();
-      } on NoSuchMethodError catch (_) {
-        throw AssertionError(
-            'Platform interfaces must not be implemented with `implements`');
-      }
-    }
+    PlatformInterface.verifyToken(instance, _token);
     _instance = instance;
   }
 
@@ -72,12 +115,4 @@ abstract class UrlLauncherPlatform {
   Future<void> closeWebView() {
     throw UnimplementedError('closeWebView() has not been implemented.');
   }
-
-  // This method makes sure that UrlLauncher isn't implemented with `implements`.
-  //
-  // See class doc for more details on why implementing this class is forbidden.
-  //
-  // This private method is called by the instance setter, which fails if the class is
-  // implemented with `implements`.
-  void _verifyProvidesDefaultImplementations() {}
 }

packages/url_launcher/url_launcher_platform_interface/pubspec.yaml

@@ -4,7 +4,7 @@ author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/url_launcher/url_launcher_platform_interface
 # NOTE: We strongly prefer non-breaking changes, even at the expense of a
 # less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
-version: 1.0.3
+version: 1.0.4
 
 dependencies:
   flutter:

packages/url_launcher/url_launcher_platform_interface/test/method_channel_url_launcher_test.dart

@@ -25,9 +25,8 @@ void main() {
     });
 
     test('Can be mocked with `implements`', () {
-      final ImplementsUrlLauncherPlatform mock =
-          ImplementsUrlLauncherPlatform();
-      when(mock.isMock).thenReturn(true);
+      final UrlLauncherPlatform mock =
+          ImplementsUrlLauncherPlatformUsingMockPlatformInterface();
       UrlLauncherPlatform.instance = mock;
     });
 
@@ -283,4 +282,8 @@ void main() {
 class ImplementsUrlLauncherPlatform extends Mock
     implements UrlLauncherPlatform {}
 
+class ImplementsUrlLauncherPlatformUsingMockPlatformInterface extends Mock
+    with MockPlatformInterface
+    implements UrlLauncherPlatform {}
+
 class ExtendsUrlLauncherPlatform extends UrlLauncherPlatform {}