@Override
  public int get(PageId pageId, int pageOffset, int bytesToRead, ReadTargetBuffer target,
      CacheContext cacheContext) {
    getOrUpdateShadowCache(pageId, bytesToRead, cacheContext);
    return mCacheManager.get(pageId, pageOffset, bytesToRead, target, cacheContext);
  }
@Test
  public void getNotExist() throws Exception {
    assertEquals(0, mCacheManager.get(PAGE_ID1, PAGE1.length, mBuf, 0));
  }