'Tags can be selectively set by namespace'

def test_set_ns(self):

    apple = self.food_model.objects.create(name='apple')
    tags_before_set = ['a:1', 'a:2', 'a:3']
    tags_after_set = ['a:4', 'a:5', 'a:6']
    tags_not_set = ['1', '2', 'b:1', 'b:2', 'c:1']
    apple.tags.add(*tags_before_set)
    apple.tags.add(*tags_not_set)
    apple.tags.set_ns('a:', *tags_after_set)
    self.assert_tags_equal(apple.tags.all(), (tags_after_set + tags_not_set))
