Escaper escaper = Escapers.builder().setUnsafeReplacement("X").build();
    assertEquals("\0\uFFFF", escaper.escape("\0\uFFFF"));
  }

  public void testBuilderRetainsState() {
    // Setting a safe range and unsafe replacement works as expected.
    Escapers.Builder builder = Escapers.builder();
    builder.setSafeRange('a', 'z');
    builder.setUnsafeReplacement("X");