### Question:
HashCache implements Cache { @Override public void put(String key, String value) throws CacheException { try { store.put(key, value); } catch (Exception e) { throw new CacheException("Cache error on put!", e); } } HashCache(); @Override String get(String key); @Override void put(String key, String value);  }### Answer:
@Test(expected = CacheException.class) public void putRaisesCacheExceptionForNull() throws Exception { cache.put(null, null); }