[&env]() { return env->NowSeconds(); });
  // Execute the first read to load the block.
  TF_EXPECT_OK(ReadCache(&cache2, "", 0, 1, &out));
  EXPECT_EQ(calls, 1);
  // Advance the clock by a huge amount and verify that the cached block is
  // used to satisfy the read.
  env->SetNowSeconds(365 * 24 * 60 * 60);  // ~1 year, just for fun.
  TF_EXPECT_OK(ReadCache(&cache2, "", 0, 1, &out));
  EXPECT_EQ(calls, 1);
}