使用mockito和@GenerateNiceMocks注解编写单元测试，尝试测试一个cubit函数，但when().thenAnswer()行似乎都不起作用。在调试测试和检查该函数的局部变量时，所有这些变量都被设置为null，而不是thenAnswer()中的变量。

测试功能

Future<void> loadStoredCredentials() async {
  String? email = await storage.read(key: AuthenticationKeys.rememberEmail);
  String? str = await storage.read(key: AuthenticationKeys.rememberMeKey);
  String? lastViewedMessages = await storage.read(
    key: 'lastViewedMessages',
  );

  bool rememberMe = false;
  if (str != null) {
    rememberMe = true;
  }

  if (email != null) {
    emit(state.copyWith(
      username: email,
      usernameValid: FieldValidity.valid,
      rememberMe: rememberMe,
      lastViewedMessages: lastViewedMessages,
    ));
  }
}

测试文件

@GenerateNiceMocks([MockSpec<FlutterSecureStorage>()])

void main() async {
  TestWidgetsFlutterBinding.ensureInitialized();

  SignInCubit? signInCubit;

  setUp(() async {
    signInCubit = SignInCubit();
  });

  group('MockFlutterSecureStorage tests -', () {
    setUpAll(() => FlutterSecureStorage.setMockInitialValues({}));

    final email = Future.value('test@test.test');
    final flag = Future.value('true');
    final nullFuture = Future.value('');

    blocTest<SignInCubit, SignInCubitState>(
      'loadStoredCredentials - success',
      build: () => SignInCubit(),
      act: (cubit) async {
        final storage = MockFlutterSecureStorage();

        when(storage.read(key: AuthenticationKeys.rememberEmail))
            .thenAnswer((_) => email);
        when(storage.read(key: AuthenticationKeys.rememberMeKey))
            .thenAnswer((_) => flag);
        when(storage.read(key: 'lastViewedMessages'))
            .thenAnswer((_) => nullFuture);

        await cubit.loadStoredCredentials();
      },
      expect: () => (isA<SignInCubitState>),
    );
  });
}

测试错误

Expected: <Closure: () => TypeMatcher<SignInCubitState> from Function 'isA': static.>
  Actual: []

package:test_api                             expect
package:bloc_test/src/bloc_test.dart 220:16  testBloc.<fn>
===== asynchronous gap ===========================
dart:async                                   _CustomZone.registerUnaryCallback
package:bloc_test/src/bloc_test.dart 201:7   testBloc.<fn>
dart:async                                   runZonedGuarded
package:bloc_test/src/bloc_test.dart 199:9   testBloc
package:bloc_test/src/bloc_test.dart 156:13  blocTest.<fn>