@GenerateMocks does not generate for void function without parameter

[EhiltonKazuo]

I'm new in mockito and null safety operators, but i followed the NULL_SAFETY_README. This is the annotation that im using:
@GenerateMocks([], customMocks: [MockSpec<LoginPresenter>(as: #LoginPresenterSpy)])

This is the sample of LoginPresenter:

abstract class LoginPresenter {
  Stream<String> get emailErrorStream;
  Stream<String> get passwordErrorStream;
  Stream<String> get mainErrorStream;
  Stream<bool> get isFormValidStream;
  Stream<bool> get isLoadingStream;

  void validateEmail(String email);
  void validatePassword(String password);
  void auth();
  void dispose();
}

And this is the generate code build_runner:

class LoginPresenterSpy extends _i1.Mock implements _i2.LoginPresenter {
  LoginPresenterSpy() {
    _i1.throwOnMissingStub(this);
  }

  @override
  _i3.Stream<String> get emailErrorStream =>
      (super.noSuchMethod(Invocation.getter(#emailErrorStream),
          returnValue: Stream<String>.empty()) as _i3.Stream<String>);
  @override
  _i3.Stream<String> get passwordErrorStream =>
      (super.noSuchMethod(Invocation.getter(#passwordErrorStream),
          returnValue: Stream<String>.empty()) as _i3.Stream<String>);
  @override
  _i3.Stream<String> get mainErrorStream =>
      (super.noSuchMethod(Invocation.getter(#mainErrorStream),
          returnValue: Stream<String>.empty()) as _i3.Stream<String>);
  @override
  _i3.Stream<bool> get isFormValidStream =>
      (super.noSuchMethod(Invocation.getter(#isFormValidStream),
          returnValue: Stream<bool>.empty()) as _i3.Stream<bool>);
  @override
  _i3.Stream<bool> get isLoadingStream =>
      (super.noSuchMethod(Invocation.getter(#isLoadingStream),
          returnValue: Stream<bool>.empty()) as _i3.Stream<bool>);
  @override
  void validateEmail(String? email) =>
      super.noSuchMethod(Invocation.method(#validateEmail, [email]),
          returnValueForMissingStub: null);
  @override
  void validatePassword(String? password) =>
      super.noSuchMethod(Invocation.method(#validatePassword, [password]),
          returnValueForMissingStub: null);
}

But doesn't exist the auth and dispose functions. Am i doing wrong?

[srawlins]

Nope; you are not doing anything wrong. Mock.noSuchMethod will handle those methods.

[mateusdeap]

I'm not sure I understand. I'm coming across a problem where I have methods similar to @EhiltonKazuo's which return void and have no parameters, and the generated mock class does not override them. Thus, when I call flutter test I get:

MissingStubError: 'start'
  No stub was found which matches the arguments of this method call:
  start()
  
  Add a stub for this method using Mockito's 'when' API, or generate the mock for MockTomato with 'returnNullOnMissingStub: true'.
  package:mockito/src/mock.dart 190:7                         Mock._noSuchMethod
  package:mockito/src/mock.dart 184:45                        Mock.noSuchMethod
  package:focus_index/domain/entities/tomato.dart 2:8         MockTomato.start
  package:focus_index/domain/usecases/start_timer.dart 11:18  StartTimer.execute
  test/usecases/start_timer_test.dart 29:13                   main.<fn>.<fn>.<fn>

By what you're saying, mockito should automatically handle these cases?

My test file looks like this, btw:

import 'package:focus_index/domain/entities/timer_controller.dart';
import 'package:focus_index/domain/entities/tomato.dart';
import 'package:focus_index/domain/usecases/start_timer.dart';
import 'package:mockito/annotations.dart';
import 'package:mockito/mockito.dart';
import 'package:test/test.dart';

import 'start_timer_test.mocks.dart';

@GenerateMocks([Tomato])
main() {
  group("Start Timer", () {
    group("execute", () {
      TimerController timerController;
      MockTomato tomato;
      StartTimer sut;

      setUp(() {
        timerController = TimerController.instance;
        tomato = MockTomato();
        sut = StartTimer(tomato);
      });

      test("should start a new tomato given the last timer was a rest period",
          () {
        timerController.increaseTomatoStreak();
        timerController.increaseRestStreak();

        sut.execute();

        verify(tomato.start());
      });

      tearDown(() {
        timerController.reset();
      });
    });
  });
}

[mateusdeap]

So I got it to pass by modifying the annotation as suggested in the NULL_SAFETY_README:
@GenerateMocks([], customMocks: [MockSpec<Tomato>(returnNullOnMissingStub: true)])

However, I don't know if this is what I should be doing since it is not the case that my method returns null. But I don't really know if a void return type is equivalent to returning null, so...

[EhiltonKazuo]

I think you only use this, if your code is legacy. I will wait the new update to solve this.

[natebosch]

However, I don't know if this is what I should be doing since it is not the case that my method returns null. But I don't really know if a void return type is equivalent to returning null, so...

This is the behavior of mockito before the null safety migration. void is a type which any value can flow into. You can return any value at all through a void return type, the value null happens to be the most common one. If you don't have an explicit return statement, a null will still be returned.

The returnNullOnMissingStub configuration could have been named something like allowMissingStubs and we chose the default of false because we think it's a better practice that behavior is explicitly stubbed instead of implicitly allowing interactions, especially since the implicit behavior can't work consistently between nullable and non-nullable return types. The name returnNullOnMissingStub is intended to make it more clear what the behavior is so that folks who are opted in to null safety understand why a non-nullable return type and a missing stub aren't compatible.

From the standpoint of avoiding magic in your tests I'd personally recommend you avoid returnNullOnMissingStub: true and explicitly stub all the behavior that gets used in your test. If you goal is to retain as much backward compatibility with the pre-migration mockito it is fine to use.

I will wait the new update to solve this.

@srawlins can correct me if I'm wrong, but I don't think we have any changes planned here. This is working as intended.

If you are using GenerateMocks you should either stub all behavior, or pass the returnNullOnMissingStub argument.

[mateusdeap]

@natebosch Thanks! So, by what I'm understanding, it would be best practice to actually return something for my methods, is that right?

[srawlins]

Actually, for #305, I did land changes to allow calling functions which return void or Future<void>, even if they have not been stubbed. The rationale is that stubbing is all about setting a return value, but regardless of the arguments passed to a void method, the "result" is... always void.

These shipped in 5.0.0-nullsafety.6. @mateusdeap can you show what version you are running?

[srawlins]

@mateusdeap I can reproduce this in a test, at HEAD; this bug slipped through the new tests that landed with that change.

[mateusdeap]

@srawlins Awesome then! I know you reproduced it at HEAD, but just for the information, I'm using 5.0.3

[flocbit]

@srawlins Is there an ETA for your fix? Experiencing the same thing as @mateusdeap...

[srawlins]

This fix has landed on HEAD. I'm waiting for internal review of one more change + a version bump, to be synced to GitHub. Likely tomorrow or Tuesday.

[MilanObrenovic]

Sorry but this still isnt fixed. My test fails because of this issue.

[srawlins]

@MilanObrenovic can you please provide:

• the version of mockito you are using
• a minimal reproduction case
• the generated mock file you see.

Since this bug is so old, you are probably hitting a new, different issue, and you should open a new issue.

[MilanObrenovic]

@MilanObrenovic can you please provide:

• the version of mockito you are using
• a minimal reproduction case
• the generated mock file you see.

Since this bug is so old, you are probably hitting a new, different issue, and you should open a new issue.

version of mockito: ^5.0.16 (latest as of now)

my test:

test("Should perform database batch delete of chat.", () async {
  // Arrange
  const String chatId = "111";
  when(mockDatabase.batch()).thenReturn(mockBatch);

  // Act
  await dataSourceImpl.deleteChat(
    chatId: chatId,
  );

  // Assert
  verifyInOrder([
    mockDatabase.batch(),
    mockBatch.delete(
      "messages",
      where: anyNamed("where"),
      whereArgs: [chatId],
    ),
    mockBatch.delete(
      "chats",
      where: anyNamed("where"),
      whereArgs: [chatId],
    ),
    mockBatch.commit(
      noResult: true,
    ),
  ]);
});

deleteChat method:

@override
Future<void> deleteChat({required String chatId}) async {
  final Batch batch = _database.batch();
  batch.delete(
    "messages",
    where: "chat_id = ?",
    whereArgs: [chatId],
  );
  batch.delete(
    "chats",
    where: "id = ?",
    whereArgs: [chatId],
  );
  await batch.commit( // <--- THE CRASH HAPPENS BECAUSE OF THIS LINE !!!
    noResult: true,
  );
}

error:

MissingStubError: 'commit'
No stub was found which matches the arguments of this method call:
commit({exclusive: null, noResult: true, continueOnError: null})

Add a stub for this method using Mockito's 'when' API, or generate the mock for MockBatch with 'returnNullOnMissingStub: true'.

The error message looks pretty straightforward.

I tried adding those optional nullable parameters "exclusive" and "continueOnError" to be non-nullable, but got the same error.

I also i tried replacing the batch with nullable on stub generation:

@GenerateMocks([Database], customMocks: [MockSpec<Batch>(returnNullOnMissingStub: true)])

But this prints a different error message:

type 'Null' is not a subtype of type 'Future<List<Object?>>' in type cast

No idea how to fix this for over several weeks. Let me know if i should create a new issue.

[srawlins]

@MilanObrenovic This is unrelated to #367.

MissingStubError: 'commit'
No stub was found which matches the arguments of this method call:
commit({exclusive: null, noResult: true, continueOnError: null})

Add a stub for this method using Mockito's 'when' API, or generate the mock for MockBatch with 'returnNullOnMissingStub: true'.

The error message looks pretty straightforward.

When you don't provide a stub, and use returnNullOnMissingStub: true, mockito will return null on a missing stub, but the commit method must return a non-nullable value.

[MilanObrenovic]

@MilanObrenovic This is unrelated to #367.

MissingStubError: 'commit'
No stub was found which matches the arguments of this method call:
commit({exclusive: null, noResult: true, continueOnError: null})

Add a stub for this method using Mockito's 'when' API, or generate the mock for MockBatch with 'returnNullOnMissingStub: true'.

The error message looks pretty straightforward.

When you don't provide a stub, and use returnNullOnMissingStub: true, mockito will return null on a missing stub, but the commit method must return a non-nullable value.

so how do i fix this crash?

[srawlins]

Did you try the other suggestion from the error?

Add a stub for this method using Mockito's 'when' API

[MilanObrenovic]

Did you try the other suggestion from the error?

Add a stub for this method using Mockito's 'when' API

but i thought i already added that with this piece of code?

when(mockDatabase.batch()).thenReturn(mockBatch);

[srawlins]

No that is stubbing the batch method of mockDatabase.

You need to stub the commit method of mockBatch.

[MilanObrenovic]

No that is stubbing the batch method of mockDatabase.

You need to stub the commit method of mockBatch.

now it worked...

when(mockBatch.commit(
  noResult: true,
)).thenAnswer((_) async => []);

solved the issue. thank you very much.