def test_front(self):
q = Queue()
assert q.front() is None
q.enqueue('A')
assert q.front() == 'A'
q.enqueue('B')
assert q.front() == 'A'
q.dequeue()
assert q.front() == 'B'
q.dequeue()
assert q.front() is None
def test_enqueue(self):
q = Queue()
q.enqueue('A')
assert q.front() == 'A'
assert q.length() == 1
q.enqueue('B')
assert q.front() == 'A'
assert q.length() == 2
q.enqueue('C')
assert q.front() == 'A'
assert q.length() == 3
assert q.is_empty() is False
def test_init(self):
q = Queue()
assert q.front() is None
assert q.length() == 0
assert q.is_empty() is True
def test_init_with_list(self):
q = Queue(['A', 'B', 'C'])
assert q.front() == 'A'
assert q.length() == 3
assert q.is_empty() is False
