def test_empty():
test_stack = stack()
assert(test_stack.empty())
test_stack.push(1)
assert(not test_stack.empty())
def test_size():
test_stack = stack()
assert(test_stack.size() == 0)
pushed_numbers = randint(1, 20)
for i in range(pushed_numbers):
test_stack.push(i)
assert(test_stack.size() == pushed_numbers)
def test_push():
test_stack = stack()
test_stack.push(0)
assert(test_stack.top() == 0)
assert(test_stack.size() == 1)
test_stack.push(1)
assert(test_stack.top() == 1)
assert(test_stack.size() == 2)
def test_top():
test_stack = stack()
assert(test_stack.top() is None)
test_stack.push(1)
assert(test_stack.top() == 1)
test_stack.push(2)
assert(test_stack.top() == 2)
def test_drop():
test_stack = stack()
test_stack.drop()
assert(test_stack.empty())
pushed_numbers = randint(10, 20)
for i in range(pushed_numbers):
test_stack.push(i)
test_stack.drop()
assert(test_stack.empty())
def test_pop():
test_stack = stack()
assert(test_stack.pop() is None)
assert(test_stack.size() == 0)
test_stack.push(1)
test_stack.push(5)
assert(test_stack.pop() == 5)
assert(test_stack.size() == 1)
assert(test_stack.pop() == 1)
assert(test_stack.size() == 0)
assert(test_stack.pop() is None)