def test_lfu():
cache = Cache()
cache['a'] = 'x'
assert len(cache) == 1
assert len(cache.queue) == 1
_ = cache['a']
assert len(cache) == 1
assert len(cache.queue) == 2
assert cache.cache['a'] == (2, 'x')
_ = cache['a']
assert len(cache) == 1
assert len(cache.queue) == 3
assert cache.cache['a'] == (3, 'x')
cache.evict_one()
assert len(cache) == 1
assert len(cache.queue) == 2
assert cache.cache['a'] == (2, 'x')
cache.evict_one()
assert len(cache) == 1
assert len(cache.queue) == 1
assert cache.cache['a'] == (1, 'x')
cache.evict_one()
assert len(cache) == 0
assert len(cache.queue) == 0
cache['a'] = 'x'
assert len(cache) == 1
assert len(cache.queue) == 1
cache['a'] = 'y'
assert len(cache) == 1
assert len(cache.queue) == 2
assert cache.cache['a'] == (2, 'y')
