Stubs should be of the type of the collaborator

[hugochinchilla]

This code should be able to run without errors

class SomeClass:
    pass

stub = Stub(SomeClass)
assert isinstance(stub, SomeClass)

spy = Spy(SomeClass)
assert isinstance(spy, SomeClass)

mock = Mock(SomeClass)
assert isinstance(mock, SomeClass)

[tobni]

https://python-doublex.readthedocs.io/en/latest/mimics.html#mimic-doubles

[hugochinchilla]

Thank you @tobni

I wonder why this is not default behavior.

[hugochinchilla]

In my opinion this should be the default behavior, I don't understand why it was separated on a decorator.

The problem I've faced because of this is what IDE automated refactors don't work well without the mimic and it's difficult to do simple refactors as rename method or change signature without having to review a lots of tests manually. When switching to mimic stubs and mocks everything works as expected, but changing all the tests is going to require a lot of effort.

Another thing I noticed is that IDE refactors work well with non mimic stubs only when using inline stubbing and mocking, so maybe there is something that can be done about non mimic Stubs and Mocks that also makes automated refactors work when using the context managers.

[davidparsson]

While you may be right, it's not hard to come up with imaginary cases where the opposite is desired as well, and I'm sure the creator had his reasons for the current behaviour.

Changing it is however a breaking change and that decision should not be made lightly.

What IDE are you using? Is that relying on isinstance checks, or is that your code?

[hugochinchilla]

I'm using pycharm professional (latest version), I don't know if it relies on isinstance checks or does introspection of any kind, but works well with Mimic and not Mimic stubs only when used with the inline API.

I have a hard time trying to imagine which kind of test could break by retaining Liskov substitution capabilities.

[davidparsson]

I’m reopening this. Getting better IDE support (without the hassle of a mypy plugin) would be nice.

Tests that for example verifies types on passed variables will start to fail if this is changed, but with a new major version and a migration guide that might be acceptable.