'Create null locator, and attempt to call set_params() on it.
Should not exception, and should raise a warning.'

def test_set_params(self):

    loc = mticker.NullLocator()
    with warnings.catch_warnings(record=True) as w:
        warnings.simplefilter(u'always')
        loc.set_params()
        assert (len(w) == 1)
