def test_discard_only_removes_one_element(a):
t = TopoSet(a)
sizes = [len(t)]
for item in a:
t.discard(item)
sizes.append(len(t))
assert all(a == b + 1 for a, b in pairwise(sizes))
def test_discarding_all_elements_results_in_an_empty_set(a):
t = TopoSet(a)
for item in a:
t.discard(item)
assert len(t) == 0
def test_discarding_an_item_not_present_silently_succeeds(a):
b = max(a) + 1
t = TopoSet(a)
t.discard(b)