Originally reported by: Ivan Smirnov (BitBucket: aldanor, GitHub: aldanor)

Is it too restrictive to assert that ids in Metafunc.parametrize must always have length? It might be more Pythonic to try and create a list of len(argvalues) elements out of ids first:

... idfn = None if callable(ids): idfn = ids ids = None if ids and len(ids) != len(argvalues): raise ValueError('%d tests specified with %d ids' %( len(argvalues), len(ids))) ...

An example use case could be something like this (enumerate the parametrized tests):

@pytest.mark.parametrize('param', ['foo', 'bar', 'baz'], ids=itertools.count()) def some_test(x): # ...

• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/759