def test_join_multiple(self):
     assert sorted(join_css_class('cls1', 'cls2 cls3').split(' ')) == [
         'cls1',
         'cls2',
         'cls3',
     ]
     assert sorted(join_css_class(
         'cls1', 'cls1 cls2').split(' ')) == ['cls1', 'cls2']
 def test_empty(self):
     assert join_css_class('cls1', None) == 'cls1'
     assert join_css_class(None, 'cls2') == 'cls2'
 def test_output(self):
     assert join_css_class('') == ''
     assert join_css_class('cls1') == 'cls1'
 def test_join_distincts(self):
     assert join_css_class('cls1', 'cls1') == 'cls1'
     assert sorted(join_css_class('cls1', 'cls2',
                                  'cls1').split(' ')) == ['cls1', 'cls2']