def test_push_pop_empty():
stack = Stack()
assert stack.empty()
stack.push(5)
assert stack.pop() == 5
assert stack.empty()
def test_capacity():
# Create a stack that can hold a single element only.
stack = Stack(1)
assert stack.empty()
stack.push(5)
# Attempting to push an additional item should fail.
with pytest.raises(TypeError) as e_info:
stack.push(6)