How do I make pytest fixtures work with decorated functions?

Question

py.test seems to fail when I decorate test functions which has a fixture as an argument.

def deco(func):

    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        return func(*args, **kwargs)

    return wrapper


@pytest.fixture
def x():
    return 0

@deco
def test_something(x):
    assert x == 0

In this simple example, I get the following error:

TypeError: test_something() takes exactly 1 argument (0 given).

Is there a way to fix this, preferably without modifying the decorator too much? (Since the decorator is used outside testing code too.)

Answer 1

It looks like functools.wraps does not do the job well enough, so it breaks py.test's introspection.

Creating the decorator using the decorator package seems to do the trick.

import decorator

def deco(func):
    def wrapper(func, *args, **kwargs):
        return func(*args, **kwargs)
    return decorator.decorator(wrapper, func)