IllegalArgumentException.class, () -> builder.refreshAfterWrite(java.time.Duration.ZERO));
  }

  @GwtIncompatible // refreshAfterWrite
  public void testRefresh_setTwice() {
    CacheBuilder<Object, Object> builder =
        CacheBuilder.newBuilder().refreshAfterWrite(3600, SECONDS);
    assertThrows(IllegalStateException.class, () -> builder.refreshAfterWrite(3600, SECONDS));
  }

    // well, it didn't blow up.
  }

  @GwtIncompatible // refreshAfterWrite
  public void testRefresh_zero() {
    CacheBuilder<Object, Object> builder = CacheBuilder.newBuilder();
    assertThrows(IllegalArgumentException.class, () -> builder.refreshAfterWrite(0, SECONDS));
  }

  @GwtIncompatible // refreshAfterWrite
  public void testRefresh_setTwice() {
    CacheBuilder<Object, Object> builder =