Utilizing nullability in relaxed mock

[hrach]

Expected Behavior

We're migrating from Mockito and one of the biggest differences is that the relaxed mock is returning always a value, even if the method has a nullable return type.

We consider it a nice feature not to redefine methods we do not care and wanna let the code handle the default, which is rather a null than empty object (list/map/0/"").

Would you be open to add this behavior to MockK (I would try to make PR)?

Since this would be a great BC break, it should be probably configurable. Ideally the same way as the relax behavior:

• via function argument (~mockk(relaxWithNulls = true))
• via project-wide configuration

Current Behavior

        class Foo {
            fun getSomething(): Int? {
                return 1
            }
        }

        val mock = mockk<Foo>(relaxed = true) 
        assertEquals(null, mock.getSomething()) // fails, returns 0 currently

[Raibaz]

Not sure about this: although it would be rather easy to implement, I think it's right for the AnyValueGenerator to return a default, non-null value for relaxed mocks.

In my opinion, it feels more Kotlin-idiomatic to return a non-null value by default and ave users explicitly specify when they want a nullable return value to be null.

I'll have to think about this.

[hrach]

I think it's right for the AnyValueGenerator to return a default, non-null value for relaxed mocks.

Maybe that's an alternative way - allow creating custom anyValueGenerator (and also pass the proper nullability information to it).

In my opinion, it feels more Kotlin-idiomatic to return a non-null value by default

I would probably disagree but yet I'd say having idiomatic unit tests is not the motivation here: we have a lot of units tests depending on this behavior and it would ease our migration a lot.

More I think about this the custom anyValueGenerator would be probably a better choice.

[Raibaz]

Makes sense, i like the approach of being able to provide a custom anyValueGenerator, thanks for this and for the PR!