private static void doTestNull(CharMatcher matcher) throws Exception {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicInstanceMethods(matcher);
  }

  public void testNoMatches() {
    doTestNoMatches(CharMatcher.none(), "blah");
    doTestNoMatches(is('a'), "bcde");
    doTestNoMatches(isNot('a'), "aaaa");
    doTestNoMatches(anyOf(""), "abcd");
    doTestNoMatches(anyOf("x"), "abcd");