### Question:
EmailProviderCache { public String getValueForThread(Long threadRootId, String columnName) { synchronized (mThreadCache) { Map<String, String> map = mThreadCache.get(threadRootId); return (map == null) ? null : map.get(columnName); } } private  EmailProviderCache(String accountUuid); static synchronized EmailProviderCache getCache(String accountUuid, Context context); String getValueForMessage(Long messageId, String columnName); String getValueForThread(Long threadRootId, String columnName); void setValueForMessages(List<Long> messageIds, String columnName, String value); void setValueForThreads(List<Long> threadRootIds, String columnName, String value); void removeValueForMessages(List<Long> messageIds, String columnName); void removeValueForThreads(List<Long> threadRootIds, String columnName); void hideMessages(List<LocalMessage> messages); boolean isMessageHidden(Long messageId, long folderId); void unhideMessages(List<? extends Message> messages); static final String ACTION_CACHE_UPDATED; }### Answer:
@Test public void getValueForUnknownThread_returnsNull() { String result = cache.getValueForThread(1L, "subject"); assertNull(result); }