TF_EXPECT_OK(ReadCache(&cache, "b", 0, 1, &out));
  // Now load a different block of file "a" at timestamp `now` + 1. When the
  // first block of "a" expires, this block should also be removed because it
  // also belongs to file "a".
  TF_EXPECT_OK(ReadCache(&cache, "a", 8, 1, &out));
  // Ensure that all blocks are in the cache (i.e. reads are cache hits).
  EXPECT_EQ(cache.CacheSize(), 24);
  EXPECT_EQ(calls, 3);