def test_none(self):
     self.assertIsNone(greeting_for_all_friends(None))
 def test_equals(self):
     self.assertEqual(greeting_for_all_friends(['Bilal']),
                      ['Hello, Bilal!'])
 def test_equals(self):
     self.assertEqual(greeting_for_all_friends(['Bilal']), ['Hello, Bilal!'])
 def test_none_2(self):
     self.assertIsNone(greeting_for_all_friends([]))