TypeError in python.py:_getobj when having a TestCase namedtuple

[languitar]

parametrizing a test function fails in case the argument for the function is only an empty list:

@pytest.mark.parametrize('test_cases', [
    ([], )
])
def test_read_write_roundtrip(test_cases):
    pass

fails with:

/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/runner.py:150: in __init__
    self.result = func()
/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/main.py:435: in _memocollect
    return self._memoizedcall('_collected', lambda: list(self.collect()))
/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/main.py:315: in _memoizedcall
    res = function()
/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/main.py:435: in <lambda>
    return self._memoizedcall('_collected', lambda: list(self.collect()))
/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/python.py:685: in collect
    self.session._fixturemanager.parsefactories(self)
/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/python.py:1969: in parsefactories
    holderobj = node_or_obj.obj
/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/python.py:351: in fget
    self._obj = obj = self._getobj()
/media/local_data/jwienke/miniconda2/envs/monitoring/lib/python2.7/site-packages/_pytest/python.py:681: in _getobj
    obj = self.parent.obj()
E   TypeError: __new__() takes exactly 4 arguments (1 given)

astroid (1.4.4)
backports.shutil-get-terminal-size (1.0.0)
backports.ssl-match-hostname (3.4.0.2)
coverage (4.1)
cycler (0.10.0)
decorator (4.0.9)
enum34 (1.1.3)
futures (3.0.5)
greenlet (0.4.9)
ipython (4.2.0)
ipython-genutils (0.1.0)
jenkinsapi (0.2.30)
junit-xml (1.6)
lazy-object-proxy (1.2.1)
loggerbyclass (0.2.0)
logilab-common (1.0.2)
matplotlib (1.5.1)
monitoring-lib (0.1.0)
msgpack-python (0.4.7)
neovim (0.1.7)
nose (1.3.7)
numexpr (2.5.2)
numpy (1.11.0)
pandas (0.18.1)
path.py (0.0.0)
patsy (0.4.1)
pep8 (1.7.0)
perfmonvalidation (0.3)
pexpect (4.0.1)
pickleshare (0.5)
pip (7.1.2)
protobuf (2.5.0)
ptyprocess (0.5)
py (1.4.31)
pybtex (0.19)
pycairo (1.10.0)
pylint (1.5.4)
pyparsing (2.1.1)
pytest (2.9.1)
python-dateutil (2.5.2)
pytz (2016.3)
requests (2.10.0)
rsb-python (0.13.0)
rsbag-python (0.13.1)
rst (0.13.0)
rstsandbox (0.13.0)
rststable (0.13.5)
scikit-learn (0.17.1)
scipy (0.17.1)
seaborn (0.7.0)
setuptools (20.7.0)
simplegeneric (0.8.1)
singledispatch (3.4.0.3)
six (1.10.0)
statsmodels (0.6.1)
tables (3.2.2)
traitlets (4.2.1)
trollius (2.1)
websocket-client (0.34.0)
wheel (0.29.0)
wrapt (1.10.6)

Running on ubuntu trusty 64 bit with miniconda python:

Python 2.7.11 :: Continuum Analytics, Inc.

[RonnyPfannschmidt]

please test with version 2.9.2, it has a fix for #510 which could be related - else i#ll have to investigate deeper,
but the example is a perfect start in any case

[languitar]

Same thing with 2.9.2.

This also happens when building the cartesian product for multiple parameters:

@pytest.mark.parametrize(
    'test_cases',
    [[],
     [TestCase('dummy', '453123', pd.DataFrame({'test': [1]}))]])
@pytest.mark.parametrize(
    'counters_by_component',
    [{},
     {'test': pd.DataFrame({'ffoo': [4]})}])
@pytest.mark.parametrize('test_time', [pd.to_datetime('now')])
def test_read_write_roundtrip(tmpdir, test_cases, counters_by_component,
                              test_time):
    pass

Results in the same exception once the respective parameter combination is reached.

[languitar]

And another case:

@pytest.mark.parametrize('foo', [None])
def test_read_write_roundtrip(foo):
    pass

[The-Compiler]

FWIW I can't reproduce either of the minimal examples with Python 2.7.11 and pytest 2.9.2.

[languitar]

So maybe it is miniconda-related?

[The-Compiler]

I'd doubt it, but maybe I'm wrong 😉

Can you run with --collect-only or do you get the same error? And you're sure you don't get it when not doing the parametrization?

[languitar]

Ok, I found what is causing this in my test file:

from perfmonvalidation.data import (TestCase)

[languitar]

I can import that with a different name, but can't the name clash be avoided?

[RonnyPfannschmidt]

__test__ = False in the class?

[The-Compiler]

Okay, so it has nothing to do with @pytest.mark.parametrize at all then?

pytest will try to collect tests in all classes starting with Test..., but I still wouldn't expect it to blow up like this. Can you show how perfmonvalidation.data.TestCase looks?

[languitar]

its a namedtuple

[The-Compiler]

Reproduced with this test_x.py:

import collections
TestCase = collections.namedtuple('TestCase', ['a'])

Renaming the issue to avoid confusion.