public void testConstants_charset() throws Exception {
    for (Field field : getConstantFields()) {
      Optional<Charset> charset = ((MediaType) field.get(null)).charset();
      if (field.getName().endsWith("_UTF_8")) {
        assertThat(charset).hasValue(UTF_8);
      } else {
        assertThat(charset).isAbsent();
      }
    }
  }

  @J2ktIncompatible
  @GwtIncompatible // reflection