gistfile1.py

def get():
    return 0

def test_foo():
    a = 42
    assert a == get()

gistfile2.txt

~ $ py.test test.py 
============================= test session starts ==============================
platform darwin -- Python 2.7.5 -- py-1.4.20 -- pytest-2.5.2
collected 1 items

test.py F

=================================== FAILURES ===================================
___________________________________ test_foo ___________________________________

    def test_foo():
        a = 42
>       assert a == get()
E       assert 42 == 0
E        +  where 0 = get()

test.py:6: AssertionError
=========================== 1 failed in 0.02 seconds ===========================