After migrating flutter code to null-safety, mock objects not accepting `any`

Question

After the release of Flutter 2, I've migrated my code to sdk: '>=2.12.0 <3.0.0' and all codes are "sound null safety" now. But I encountered errors in unit tests with mockito 5.0.0

e.g:

when(mockClient.login(any)).thenThrow(GrpcError.unavailable());

was ok earlier, but now, the compiler shows an error under any, indicating: The argument type 'Null' can't be assigned to the parameter type 'LoginRequest'

I read this link from mockito repo but I hope there is an easier way to write tests for methods with "not nullable" arguments like before.

Answer 1

When assigning the Mock object, it needs to be of the Mock object type, not the BaseClass.

@GenerateMocks(MockSpec<ITransactionRepository>(as: #MockTransactionRepository),
)
void main()
{
    ....
    ITransactionRepository baseObject = MockTransactionRepository();           // wrong
    MockTransactionRepository mockObject = MockTransactionRepository();   // right
    when(baseObject.method(any));     // results in compile error
    when(mockObject.method(any)); // OK
    ...
}

Source: https://github.com/dart-lang/mockito/issues/364

Answer 2

See the solution here. You can use the mocktail package which makes it way easier.

With mocktail your code would become

when(() => mockClient.login(any())).thenThrow(GrpcError.unavailable());