### Question:
ListMemoizer { public boolean remove(final ListNode<T> list) { if (null == list) { throw new IllegalArgumentException("null key"); } return !list.isNil() && null != helper && helper.remove(list); } ListMemoizer(final Comparator<T> comparator); M get(final ListNode<T> list); boolean put(final ListNode<T> list, final M memo); boolean remove(final ListNode<T> list);  }### Answer:
@Test public void testRemove() throws Exception { ListMemoizer<String, Integer> m = createMemoizer(); assertFalse(m.remove(createList("foo"))); assertFalse(m.remove(createList("foo", "bar"))); assertFalse(m.remove(createList())); m.put(createList("1", "2", "3", "4"), 0); m.put(createList("one", "two", "three"), 1); m.put(createList("a", "b"), 2); assertFalse(m.remove(createList("one"))); assertFalse(m.remove(createList("one", "two"))); assertEquals((Integer) 1, m.get(createList("one", "two", "three"))); assertTrue(m.remove(createList("one", "two", "three"))); assertNull(m.get(createList("one", "two", "three"))); assertEquals((Integer) 0, m.get(createList("1", "2", "3", "4"))); assertTrue(m.remove(createList("1", "2", "3", "4"))); assertNull(m.get(createList("1", "2", "3", "4"))); m.put(createList("one", "two", "three"), 42); assertEquals((Integer) 42, m.get(createList("one", "two", "three"))); }