How to type hint class defined in conftest and returned from fixture

Question

I have a class that I want to use in various test cases/files to test certain conditions. Something like the following:

class MyTester:
  @staticmethod
  def does_string_apply(my_string: str) -> bool:
    return my_string == 'Hello World'

I want to use that class in various test cases among various test files, which is why I defined it in conftest and provided a fixture to access that class.

@pytest.fixture(name=my_tester)
def fixture_my_tester() -> type[MyTester]:
  return MyTester

That fixture is used in the test cases, but the class name is not imported. Therefore, I do not know how to type hint the fixture:

def test_something(my_tester: type['What goes here?']) -> None:
   assert my_tester.does_string_apply("Hello")

Answer 1

So just a bit of background on Pytest for future readers - in a test you can specify an argument name, that can connect to a fixture in a different file, so the class may not necessarily need to be imported (outside of typing).

The short answer is, simply:

from .conftest import MyTester

It may be that conftest isn't accessible in this way, in which case you could put MyTester into a utils section of the package.

If circular imports are a concern with the testing system, you can also import it like this:

if typing.TYPE_CHECKING:
    from .conftest import MyTester

I get the feeling that pytest was not originally designed with typing in mind, but it does expose enough options that it's possible to make it work. Hope this helps!