def test_clear(self):
ss = StackSet()
ss.push(3)
ss.push(5)
ss.clear()
assert len(ss) == 0
ss.push(1)
ss.push(9)
assert len(ss) == 2
ss.clear()
assert len(ss) == 0
assert not 3 in ss
assert not 5 in ss
assert not 1 in ss
assert not 9 in ss
