### Question:
AbstractFileCache { public synchronized boolean containsKey(K key) { return this.getCacheFile(key).exists(); } protected  AbstractFileCache(File cacheDirectory, String prefix, String suffix, final int maxAgeInSeconds); synchronized void clear(); synchronized boolean containsKey(K key); synchronized byte[] get(K key); synchronized InputStream getAsInputStream(K key); File getCacheDirectory(); File getCacheFile(K key); synchronized void purge(); synchronized void put(K key, byte[] value); synchronized void putFile(K key, File file, boolean move); synchronized void remove(K key);  }### Answer:
@Test public void testContainsKey() throws CacheException { byte[] testBytes = "test".getBytes(StandardCharsets.US_ASCII); underTest.put("test", testBytes); assertTrue(underTest.containsKey("test")); }