def test_get_should_return_value_and_move_node_to_front(self):
"""
LRU_Cache::get() should return the value and move the node to the front (MRU) position
of the linked list.
"""
# Set up.
cache = LRU_Cache(5)
test_data = {
'udacity': 1,
'python': 2,
100: 'hello world',
200: 'algorithms'
}
for key, value in test_data.items():
cache.set(key, value)
# Test -1 is returned if the key does not exist.
self.assertEqual(-1, cache.get('does_not_exist'))
# Test getting the value and that the node was moved to the front (MRU) position.
self.assertEqual('hello world', cache.get(100))
node = cache.head.next
self.assertEqual(cache.hashtable[100], node)
self.assertEqual('hello world', node.value)
self.assertEqual(100, node.key)
self.assertEqual(2, cache.get('python'))
node = cache.head.next
self.assertEqual(cache.hashtable['python'], node)
self.assertEqual(2, node.value)
self.assertEqual('python', node.key)
self.assertEqual(1, cache.get('udacity'))
node = cache.head.next
self.assertEqual(cache.hashtable['udacity'], node)
self.assertEqual(1, node.value)
self.assertEqual('udacity', node.key)
self.assertEqual('algorithms', cache.get(200))
node = cache.head.next
self.assertEqual(cache.hashtable[200], node)
self.assertEqual('algorithms', node.value)
self.assertEqual(200, node.key)
# Clean up.
cache.clear()
def test_set_should_cache_the_new_node(self):
"""
LRU_Cache::set() should cache (add) the new node.
"""
# Set up.
cache = LRU_Cache(5)
test_data = {
'udacity': 1,
'python': 2,
100: 'hello world',
200: 'algorithms'
}
# Test set stores each item.
for key, value in test_data.items():
self.assertFalse(key in cache.hashtable)
cache.set(key, value)
self.assertTrue(key in cache.hashtable)
# Test each node in the linked list.
node = cache.head.next
self.assertEqual(cache.hashtable[200], node)
self.assertEqual('algorithms', node.value)
self.assertEqual(200, node.key)
node = node.next
self.assertEqual(cache.hashtable[100], node)
self.assertEqual('hello world', node.value)
self.assertEqual(100, node.key)
node = node.next
self.assertEqual(cache.hashtable['python'], node)
self.assertEqual(2, node.value)
self.assertEqual('python', node.key)
node = node.next
self.assertEqual(cache.hashtable['udacity'], node)
self.assertEqual(1, node.value)
self.assertEqual('udacity', node.key)
# Test the tail node.
self.assertEqual(cache.hashtable['udacity'], cache.tail.prev)
# Clean up.
cache.clear()
def test_set_should_remove_lru_node_when_overcapacity(self):
"""
LRU_Cache::set() should remove the LRU node when overcapacity.
"""
# Set up.
cache = LRU_Cache(4)
test_data = {
'udacity': 1,
'python': 2,
100: 'hello world',
200: 'algorithms'
}
for key, value in test_data.items():
cache.set(key, value)
# Check the before states.
self.assertEqual(cache.hashtable['udacity'], cache.tail.prev)
self.assertEqual(len(cache.hashtable), cache.capacity)
cache.set(300, 'overcapacity')
# Test that the previous last node has been removed.
self.assertEqual(len(cache.hashtable), cache.capacity)
self.assertFalse('udacity' in cache.hashtable)
self.assertEqual(-1, cache.get('udacity'))
self.assertEqual(cache.hashtable['python'], cache.tail.prev)
# Retest each node in the linked list.
node = cache.head.next
self.assertEqual(cache.hashtable[300], node)
self.assertEqual(cache.hashtable[200], node.next)
self.assertEqual(cache.hashtable[100], node.next.next)
self.assertEqual(cache.hashtable['python'], node.next.next.next)
# Clean up.
cache.clear()
def test_set_should_overwrite_existing_nodes(self):
"""
LRU_Cache::set() should overwrite existing nodes and move the node to the front (MRU) position
of the linked list.
"""
# Set up.
cache = LRU_Cache(5)
test_data = {
'udacity': 1,
'python': 2,
100: 'hello world',
200: 'algorithms'
}
for key, value in test_data.items():
cache.set(key, value)
#
# Test a node in the middle.
#
# Test set overwrites value in the existing node.
prev_number_items = len(cache.hashtable)
self.assertEqual(2, cache.hashtable['python'].value)
cache.set('python', 20)
self.assertEqual(20, cache.hashtable['python'].value)
self.assertEqual(prev_number_items, len(cache.hashtable))
# Test that the node was moved to the MRU position.
node = cache.head.next
self.assertEqual(cache.hashtable['python'], node)
self.assertEqual(20, node.value)
self.assertEqual('python', node.key)
# Test the wiring in the rest of the linked list.
node = node.next
self.assertEqual(cache.hashtable[200], node)
self.assertEqual('algorithms', node.value)
self.assertEqual(200, node.key)
node = node.next
self.assertEqual(cache.hashtable[100], node)
self.assertEqual('hello world', node.value)
self.assertEqual(100, node.key)
node = node.next
self.assertEqual(cache.hashtable['udacity'], node)
self.assertEqual(1, node.value)
self.assertEqual('udacity', node.key)
self.assertEqual(cache.hashtable['udacity'], cache.tail.prev)
#
# Test the last node.
#
# Test set overwrites value in the existing node.
prev_number_items = len(cache.hashtable)
self.assertEqual(1, cache.hashtable['udacity'].value)
cache.set('udacity', 10)
self.assertEqual(10, cache.hashtable['udacity'].value)
self.assertEqual(prev_number_items, len(cache.hashtable))
# Test that the node was moved to the MRU position.
node = cache.head.next
self.assertEqual(cache.hashtable['udacity'], node)
self.assertEqual(10, node.value)
self.assertEqual('udacity', node.key)
node = node.next
self.assertEqual(cache.hashtable['python'], node)
self.assertEqual(20, node.value)
self.assertEqual('python', node.key)
# Test the wiring in the rest of the linked list.
node = node.next
self.assertEqual(cache.hashtable[200], node)
self.assertEqual('algorithms', node.value)
self.assertEqual(200, node.key)
node = node.next
self.assertEqual(cache.hashtable[100], node)
self.assertEqual('hello world', node.value)
self.assertEqual(100, node.key)
self.assertEqual(cache.hashtable[100], cache.tail.prev)
# Clean up.
cache.clear()