### Question:
SimpleCachedDaoImpl implements SimpleCachedDao<K, V> { @Override public void invalidateCache() { cache.clear(); } SimpleCachedDaoImpl(); @Override V update(@Nonnull final K key, @Nullable final V value); @Override Optional<V> find(@Nonnull final K key); @Override void invalidateCache(); @Override boolean isEmpty(); @Override Iterable<V> values(); @Override Iterable<K> keySet();  }### Answer:
@Test public void testInvalidateCache() throws Exception { dao.update(KEY_1, DUMMY_DATA_1); Assert.assertTrue(dao.find(KEY_1).isPresent()); dao.invalidateCache(); Assert.assertFalse(dao.find(KEY_1).isPresent()); }