Passing global variable from test function

[kescobo]

Just posted over at SO, but thought I would do so here as well.

I have a function in a module that depends on a global variable, and I'd like to test this function using pytest. But when the function gets to the global variable, it says it's not defined. Note: the function works fine when I test it manually. Here's a minimal example that illustrates the problem.

In the file scratch.py I have:

def bar():
    global flag
    if flag:
        return 1
    else:
        return 0

Then, in scratch_test.py I have:

import pytest
import scratch

def test_foo():
    global flag
    flag = True
    assert scratch.bar() == 1

Now, from the command line:

$ pytest scratch_test.py 
=============================================================== test session starts ===============================================================
platform darwin -- Python 3.6.0, pytest-3.1.1, py-1.4.34, pluggy-0.4.0
rootdir: /Users/ksb/computation/science/kvasir, inifile:
collected 1 items 

scratch_test.py F

==================================================================== FAILURES =====================================================================
____________________________________________________________________ test_foo _____________________________________________________________________

    def test_foo():
        global flag
        flag = True
>       assert scratch.bar() == 1

scratch_test.py:7: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

    def bar():
        global flag
>       if flag:
E       NameError: name 'flag' is not defined

scratch.py:3: NameError
============================================================ 1 failed in 0.03 seconds =============================================================
KEVINs-MacBook-Pro-2:kvasir ksb$ 

But, if I do $ python scratch_test.py I get no error, it runs fine.

So is the global variable not being passed during testing for some reason? I searched the pytest docs, and SO but didn't find anything that seems relevant.

[kescobo]

Wait - something else is wrong... sorry. Will come back and edit if I figure that out.

[RonnyPfannschmidt]

@kescobo scratch.flag = True should work for you - its commonly suggested not to use globals in such a way as it will add maintenance cost and trouble somewhere down the tile

[kescobo]

@RonnyPfannschmidt Thanks! That's actually the solution I think I needed. After some digging, I arrived at the fact that what I was doing is not recommended - the confusion comes from the fact that it was working when I did the same design pattern in the script, or so it seems.

In any case, I'll let the mystery hang and just do some reworking.