// one second of wall time), it should remove "a" and leave "b" alone.
  uint64 start = Env::Default()->NowSeconds();
  do {
    Env::Default()->SleepForMicroseconds(100000);
  } while (cache.CacheSize() == 24 && Env::Default()->NowSeconds() - start < 3);
  // There should be one block left in the cache, and it should be the first
  // block of "b".
  EXPECT_EQ(cache.CacheSize(), 8);

    // This is usually unnecessary, but we've experienced the occasional test
    // failure when testing async mode with no explicit forwarding.
    for (int i = 0; i < 100000; ++i) {
      TFE_Op* add_op_dummy = AddOp(ctx, m, m);
      TFE_OpSetDevice(add_op_dummy, cpu_device_name.c_str(), status);
      ASSERT_EQ(TF_OK, TF_GetCode(status)) << TF_Message(status);