def test_ConcatSublist(self): self.assertEqual(concat(['a','b','c', 'a'], 1, 2), 'bc')
def test_Concat(self): self.assertEqual(concat(['a','b','c'], 0, 2), 'abc')
def test_ConcatEmptyArray(self): self.assertEqual(concat([], 0, 2), '')
def test_ConcatNoneArray(self): self.assertEqual(concat(None, 0, 2), '')
def test_ConcatOutOfBoundIndex(self): self.assertEqual(concat(['a','b','c'], -1, 3), '')
def test_ConcatStartIndexGreaterThanEndIndex(self): self.assertEqual(concat(['a','b','c'], 1, 0), '')