This is supposed to fail, right?  Perhaps a separate function that asserts that creation fails should be implemented, to make it more clear?  Because if I remember correctly, the ValueError just means that the number differs from expected, but not that all of them failed.

In any case though, probably `self.assertRaises(<exception>, <callable>, *args, **kwargs)` is preferred over the try/except/pass construction in tests, because it would look more actively like asserting something (it would also fail, if that error were not raised).  :)