MediaType mediaType = MediaType.parse("text/plain");
    assertThrows(
        NullPointerException.class,
        () -> mediaType.withParameters("a", Arrays.asList((String) null)));
  }

  public void testWithCharset() {
    assertEquals(
        MediaType.parse("text/plain; charset=utf-8"),
        MediaType.parse("text/plain").withCharset(UTF_8));
    assertEquals(
        MediaType.parse("text/plain; charset=utf-8"),