How to have two issued fixtures depend on each other?

Question

In test_something(), the app instance should be the same as used by the login instance.

@pytest.fixture
def app():
    # ...
    return app

@pytest.fixture
def login(app):
    # ...
    return login

def test_something(self, app, login):
    pass

What I tried is returning both objects from the second fixture, but I wouldn't call this idiomatic.

@pytest.fixture
def app_and_login(app):
    # ...
    return app, login

def test_something(self, app_and_login):
    app, login = login_and_login

Is there a better way to do this?

Answer 1

As you described, the fixture already is shared for the runtime of the test by default.

This isn't really documented explicitly anywhere (or at least I haven't found it), but it's somewhat implicit: Sharing a fixture across tests in a module describes the scope parameter, and the default scope is function.

Other scopes would e.g. be module (share/cache the fixture for all tests in the same module) or session (cache the fixture for the whole test session).