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) 

Answer 2

Fixture feature depends on test function signature.

If you can change wrapper signature as follow, it will works.

def deco(func):     @functools.wraps(func)     def wrapper(x):         return func(x)     return wrapper 

If you can't change it, make another decorator:

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

And decorate test_somthing with deco_x:

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