def test_size_returns_the_number_of_elements_in_the_stack():
stack = Stack()
stack.push(42)
stack.push(42)
stack.push(42)
assert stack.size == 3
def test_push_increases_the_stack_size():
stack = Stack()
previous_size = stack.size
stack.push(42)
assert stack.size == (previous_size + 1)
def test_stack_push_pop_with_elements(self):
stack = Stack()
stack.push(1)
stack.push(2)
stack.push(5)
assert stack.pop() == 5
assert stack.pop() == 2
assert stack.pop() == 1
def test_peek_does_not_change_the_stack_size():
stack = Stack()
stack.push(42)
previous_size = stack.size
stack.peek()
assert stack.size == previous_size
def test_pop_decreases_the_stack_size():
stack = Stack()
stack.push(42)
previous_size = stack.size
stack.pop()
assert stack.size == (previous_size - 1)
def test_is_empty(self):
stack = Stack()
assert stack.is_empty() is True
stack.push(1)
assert stack.is_empty() is False
stack.pop()
assert stack.is_empty() is True
def test_push_items(self):
stack = Stack()
tests = [1, '0', Stack, lambda x: x, {}, [], None]
for test in tests:
stack.push(test)
assert len(tests) == len(stack)
def test_size(self):
stack = Stack()
assert len(stack) == 0
stack.push(1)
assert len(stack) == 1
stack.pop()
assert len(stack) == 0
def test_stack_as_string(self):
stack = Stack()
assert str(stack) == ''
stack.push(3)
stack.push(1)
stack.push(2)
assert repr(stack) == '2 -> 1 -> 3'
def test_pop_items(self):
stack = Stack()
with self.assertRaises(StackPopException):
stack.pop()
one = 1
two = 2
stack.push(one)
stack.push(two)
assert len(stack) == 2
assert stack.pop() == two
assert stack.pop() == one
assert len(stack) == 0
def test_str_prints_the_stack_and_its_elements():
stack = Stack()
stack.push(42)
stack.push("Second element")
stack.push(True)
assert str(stack) == "Stack(True, 'Second element', 42)"
def test_is_empty_returns_false_on_stack_with_elements():
stack = Stack()
stack.push(42)
assert not stack.is_empty()
def test_push_sets_the_element_on_top():
stack = Stack()
stack.push(42)
assert stack.peek() == 42
def test_peek_returns_the_element_on_top():
stack = Stack()
stack.push(42)
assert stack.peek() == 42
def test_pop_returns_the_latest_element_pushed():
stack = Stack()
stack.push("First")
stack.push(42)
assert stack.pop() == 42