### Question:
UserContextStoreImpl implements UserContextStore { @Override public boolean containsKey(String contextId) { return userContextMap.containsKey(contextId); } UserContextStoreImpl(); @Override String get(String contextId); @Override void put(String contextId, String context); @Override boolean containsKey(String contextId); @Override void remove(String contextId);  }### Answer:
@Test public void testContainsKey() throws Exception { userContextStore.put(CACHE_KEY, CACHE_VALUE); Assert.assertTrue(userContextStore.containsKey(CACHE_KEY)); Thread.sleep(2500); Assert.assertFalse(userContextStore.containsKey(CACHE_KEY)); }