def test_interpose():
assert "a" == first(rest(interpose("a", range(1000000000))))
assert "tXaXrXzXaXn" == "".join(interpose("X", "tarzan"))
assert list(interpose(0, itertools.repeat(1, 4))) == [1, 0, 1, 0, 1, 0, 1]
assert list(interpose('.', ['a', 'b', 'c'])) == ['a', '.', 'b', '.', 'c']
def test_rest():
assert list(rest('ABCDE')) == list('BCDE')
assert list(rest((3, 2, 1))) == list((2, 1))
