pytest如何处理调用其他灯具的灯具？

Question

I have two pytest fixtures, client and app . client calls app .

The test function test_register has arguments client and app and hence calls both fixtures.

My question is if the instance of app used in test_register is always going to be the one that client called, and if this is how pytest works in general (the assertion in test_register passes, so it is true in this case) .

In other words, does pytest generate unrelated instances for each argument in a test function that calls a fixture or does it call the fixtures and the instances returned also reference each other?

Here's the code:

@pytest.fixture
def app():
    app = create_app({
        'TESTING': True,
    })

    yield app


@pytest.fixture
def client(app):
    return app.test_client()



def test_register(client, app):
    assert client.application is app

Answer 1

All fixtures have a scope, the implicit scope being function but there's also class , module and session scopes. Within each scope there will only ever be one instance created of a fixture.

So in your example both app and client are using the function-scope. When executing test_register it enters the function-scope of this test and creates the fixture intances. Hence both test_register and client get the same instance of app .

See the docs for more details on how this all works.