Documentation: Throws type 'Null' is not a subtype of type 'SomeType'

[morrowyn]

Hi,

I greatly appreciate the work that you are doing for the fluttter community. Especially since the null-safety and creating a better tool than mockito.

I ran into the following issue when porting from mockito to mocktail, whereas mockito somehow skipped non-mocked methods because of being null.

I received this error:

Throws type 'Null' is not a subtype of type 'Future<void>'

Now it took me a while to figure out what was happening, so maybe you could add a small paragraph explaining what to do when hitting this error when porting your mockito code to mocktail.

Eg. something like this:

When you receive the following error:

Throws type 'Null' is not a subtype of type 'SomeType'

This error means you need to add a when(() => mock.missingMockMethod()).thenAnswer((_) => yourAnswer) on that particular method of your mock you are using, since mockito kindly skipped this for you because it was null in the pre-null-safety era.

[vlad-ed-git]

The FAQ explanation is not clear.

I have for you here the solution offered.
To address this, we must explicitly stub sleep like:

final person = MockPerson();
when(person.sleep).thenAnswer((_) async {});

Here is the issue (s):

1. Do we not always stub? If you scroll up on the documentation, it literally says Stub and Verify . The FAQ solution is written as if we often do not stub or that stubbing is done implicitly. But the difference between this explicit stubbing and what is already the norm is not clear.
2. when(person.sleep). . sleep here is written not as a method call. Is this a typo? should it be person.sleep()? If this is not a typo, what is the correct way to explicitly stub sleep if sleep had parameters?

[avbk]

I just stumbeld over this issue, too. We have a method that takes a parameter and returns a future, just as @vlad-ed-git described in case 2.

Do you have any suggestion about how we could handle methods like this?

[J0B10]

Might be a bit late to the cake but i can help on the question from @avbk with an example from one of my repos:

when(() => apiMock.getAllHeatingInfo(any())).thenAnswer((_) async {});

getAllHeatingInfo() takes a string as parameter and returns Future<void>.

And addressing @vlad-ed-git: when(person.sleep) is just a shorter way to write when(() => person.sleep()). In both cases the parameter is a function that takes no parameters and runs person.sleep() when called.

When working with mocktail on a recent project I had this issue quiet often and found it annoying to always write out thenAnswer((_) async {}). Therefore I quickly defined an extension:

extension MockAsync on When<Future<void>> {
  void thenDoNothing() => thenAnswer((_) async {});
}

This made my code from above a lot quicker and less anoying to write and I think it also makes it easier to read:

when(() => apiMock.getAllHeatingInfo(any())).thenDoNothing();

@felangel Any chance something like that could make it into mocktail?