assertThrows(
        IllegalArgumentException.class, () -> builder.expireAfterWrite(Duration.ofSeconds(-1)));
  }

  @SuppressWarnings("ReturnValueIgnored")
  public void testTimeToLive_small() {
    CacheBuilder.newBuilder().expireAfterWrite(1, NANOSECONDS).build(identityLoader());
    // well, it didn't blow up.
  }

  public void testTimeToLive_setTwice() {