def test_pair_split_two_pair(self): self.assertEqual(pair_split(split_words('hello hell as dogs cats')), [('hello', 'dogs'), ('hell', 'cats')])
def test_pair_split_two(self): self.assertEqual(pair_split(split_words('hello as hell')), [('hello', 'hell')])
def test_pair_split_three(self): self.assertEqual(pair_split(split_words('hello as hell dogs as cats')), [('hello', 'hell'), ('dogs', 'cats')])
def test_pair_split_empty(self): self.assertEqual(pair_split([]), [])
def test_pair_split_one(self): self.assertEqual(pair_split(split_words('hello')), [('hello', None)])