### Question:
BidirectionalHashMap { public Map<K, V> forward() { return Collections.unmodifiableMap(keyToValue); } BidirectionalHashMap(Map<K, V> keyToValue); Map<K, V> forward(); Map<V, K> reversed();  }### Answer:
@Test public void testForward() throws Exception { BidirectionalHashMap<Integer, String> testee = new BidirectionalHashMap<>(integerStringMap); assertEquals(integerStringMap, testee.forward()); }