def test_trailing_by_two_iterator_on_collection_of_two_gives_empty_iterator():
s = [6, 9]
iter_p, iter_q = offset_iterators(s, -2)
ps = list(iter_p)
qs = list(iter_q)
assert ps == []
assert qs == [6, 9]
def test_offset_iterators_on_empty_iterable_with_zero_offset():
s = []
p, q = offset_iterators(s, 0)
with raises(StopIteration):
next(p)
with raises(StopIteration):
next(q)
def test_trailing_by_two_iterator_on_non_empty_collection():
s = [6, 9, 3, 2, 1]
iter_p, iter_q = offset_iterators(s, -2)
ps = list(iter_p)
qs = list(iter_q)
assert ps == [3, 2, 1]
assert qs == [6, 9, 3, 2, 1]
def test_leading_by_one_iterator_on_non_empty_collection():
s = [6, 9, 3, 2, 1]
iter_p, iter_q = offset_iterators(s, 1)
ps = list(iter_p)
qs = list(iter_q)
assert ps == [6, 9, 3, 2, 1]
assert qs == [9, 3, 2, 1]
def test_trailing_by_three_iterator_on_too_short_collection_raises_value_error(
):
s = [6, 9]
with raises(ValueError):
offset_iterators(s, -3)
def test_zero_offset_iterators_on_non_empty_collection_yield_identical_items():
s = [6, 9, 3, 2, 1]
iter_p, iter_q = offset_iterators(s, 0)
assert all(p == q for p, q in zip(iter_p, iter_q))