def test_push_pop(self):
p = PriorityQueue()
assert p.heap.items == []
p.enqueue('A', 2)
assert p.heap.items == [(2, 'A')]
p.enqueue('B', 2)
assert p.heap.items == [(2, 'A'), (2, 'B')]
p.enqueue('C', 1)
assert p.heap.items == [(1, 'C'), (2, 'B'), (2, 'A')]
p.enqueue('D', 1)
assert p.heap.items == [(1, 'C'), (1, 'D'), (2, 'A'), (2, 'B')]
p.enqueue('E', 3)
assert p.heap.items == [(1, 'C'), (1, 'D'), (2, 'A'), (2, 'B'),
(3, 'E')]
p.enqueue('F', 2)
assert p.heap.items == [(1, 'C'), (1, 'D'), (2, 'A'), (2, 'B'),
(3, 'E'), (2, 'F')]
assert p.push_pop('G', 1) == 'C'
assert p.heap.items == [(1, 'D'), (1, 'G'), (2, 'A'), (2, 'B'),
(3, 'E'), (2, 'F')]
assert p.push_pop('H', 2) == 'D'
assert p.heap.items == [(1, 'G'), (2, 'B'), (2, 'A'), (2, 'H'),
(3, 'E'), (2, 'F')]
assert p.push_pop('I', 3) == 'G'
assert p.heap.items == [(2, 'A'), (2, 'B'), (2, 'F'), (2, 'H'),
(3, 'E'), (3, 'I')]
assert p.push_pop('J', 4) == 'A'
assert p.heap.items == [(2, 'B'), (2, 'H'), (2, 'F'), (4, 'J'),
(3, 'E'), (3, 'I')]
assert p.push_pop('K', 1) == 'B'
assert p.heap.items == [(1, 'K'), (2, 'H'), (2, 'F'), (4, 'J'),
(3, 'E'), (3, 'I')]
assert p.push_pop('L', 3) == 'K'
assert p.heap.items == [(2, 'F'), (2, 'H'), (3, 'I'), (4, 'J'),
(3, 'E'), (3, 'L')]
