py.test -k problem

run.out

============================= test session starts ==============================
platform darwin -- Python 2.7.6 -- py-1.4.20 -- pytest-2.5.2
plugins: xdist
collected 9 items

test_example.py ..F......

=================================== FAILURES ===================================
__________________________ test_multiple_params[4-3] ___________________________

foo = 3, bar = 4

    @pytest.mark.parametrize('foo', [1, 2, 3])
    @pytest.mark.parametrize('bar', [4, 5, 6])
    def test_multiple_params(foo, bar):
>       assert foo + 1 != bar
E       assert (3 + 1) != 4

test_example.py:6: AssertionError
====================== 1 failed, 8 passed in 0.02 seconds ======================
============================= test session starts ==============================
platform darwin -- Python 2.7.6 -- py-1.4.20 -- pytest-2.5.2
plugins: xdist
collected 9 items
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/main.py", line 81, in wrap_session
INTERNALERROR>     doit(config, session)
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/main.py", line 117, in _main
INTERNALERROR>     config.hook.pytest_collection(session=session)
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/core.py", line 377, in __call__
INTERNALERROR>     return self._docall(methods, kwargs)
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/core.py", line 388, in _docall
INTERNALERROR>     res = mc.execute()
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/core.py", line 289, in execute
INTERNALERROR>     res = method(**kwargs)
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/main.py", line 121, in pytest_collection
INTERNALERROR>     return session.perform_collect()
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/main.py", line 520, in perform_collect
INTERNALERROR>     config=self.config, items=items)
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/core.py", line 377, in __call__
INTERNALERROR>     return self._docall(methods, kwargs)
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/core.py", line 388, in _docall
INTERNALERROR>     res = mc.execute()
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/core.py", line 289, in execute
INTERNALERROR>     res = method(**kwargs)
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/mark.py", line 67, in pytest_collection_modifyitems
INTERNALERROR>     if keywordexpr and not matchkeyword(colitem, keywordexpr):
INTERNALERROR>   File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/_pytest/mark.py", line 149, in matchkeyword
INTERNALERROR>     return eval(keywordexpr, {}, mapping)
INTERNALERROR>   File "<string>", line 1
INTERNALERROR>     test_multiple_params[3not 4]
INTERNALERROR>                               ^
INTERNALERROR> SyntaxError: invalid syntax

===============================  in 0.01 seconds ===============================

run.sh

py.test test_example.py

# We see that one case fails, test_multiple_params[3-4]. Let's try to re-run that case:

py.test test_example.py -k 'test_multiple_params[3-4]'

# The -k expression interpreter sees '-' as an operator

test_example.py

import pytest

@pytest.mark.parametrize('foo', [1, 2, 3])
@pytest.mark.parametrize('bar', [4, 5, 6])
def test_multiple_params(foo, bar):
    assert foo + 1 != bar