'A SimpleListFilter lookups method can return None but disables the
filter completely.'

def test_simplelistfilter_with_none_returning_lookups(self):

    modeladmin = DecadeFilterBookAdminWithNoneReturningLookups(Book, site)
    request = self.request_factory.get(u'/', {})
    changelist = self.get_changelist(request, Book, modeladmin)
    filterspec = changelist.get_filters(request)[0]
    self.assertEqual(len(filterspec), 0)
