A failing test will provide helpful output as to what went wrong:
# projectroot/tests/test_code.py
from module import code
def test_add__failing():
assert code.add(10, 11) == 33
Results:
$ py.test
================================================== test session starts ===================================================
platform darwin -- Python 2.7.10, pytest-2.9.2, py-1.4.31, pluggy-0.3.1
rootdir: /projectroot, inifile:
collected 1 items
tests/test_code.py F
======================================================== FAILURES ========================================================
___________________________________________________ test_add__failing ____________________________________________________
def test_add__failing():
> assert code.add(10, 11) == 33
E assert 21 == 33
E + where 21 = <function add at 0x105d4d6e0>(10, 11)
E + where <function add at 0x105d4d6e0> = code.add
tests/test_code.py:5: AssertionError
================================================ 1 failed in 0.01 seconds ================================================