### Question:
Trie { public boolean isEmpty() { return root == null; } Trie(); void insert(String word); boolean delete(String word); boolean containsNode(String word); boolean isEmpty();  }### Answer:
@Test public void whenEmptyTrie_thenNoElements() { Trie trie = new Trie(); assertFalse(trie.isEmpty()); }
@Test public void givenATrie_whenAddingElements_thenTrieNotEmpty() { Trie trie = createExampleTrie(); assertFalse(trie.isEmpty()); }