CacheBuilder<Object, Object> builder1 = CacheBuilder.newBuilder().weakKeys();
    assertThrows(IllegalStateException.class, () -> builder1.weakKeys());
  }

  @GwtIncompatible // weakValues
  public void testValueStrengthSetTwice() {
    CacheBuilder<Object, Object> builder1 = CacheBuilder.newBuilder().weakValues();
    assertThrows(IllegalStateException.class, () -> builder1.weakValues());