doTestEmpty(noneOf("CharMatcher"));
    doTestEmpty(inRange('n', 'q'));
    doTestEmpty(forPredicate(Predicates.equalTo('c')));
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNull() throws Exception {
    doTestNull(CharMatcher.any());
    doTestNull(CharMatcher.none());
    doTestNull(is('a'));
    doTestNull(isNot('a'));
    doTestNull(anyOf(""));
    doTestNull(anyOf("x"));

          public void tearDown() {
            Thread.interrupted();
          }
        });
  }

  @Override
  protected void tearDown() {
    tearDownStack.runTearDown();
  }

  public void testNull() throws Exception {
    new NullPointerTester()
        .setDefault(CountDownLatch.class, new CountDownLatch(0))
        .setDefault(Semaphore.class, new Semaphore(999))

    doTestEmpty(noneOf("CharMatcher"));
    doTestEmpty(inRange('n', 'q'));
    doTestEmpty(forPredicate(Predicates.equalTo('c')));
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNull() throws Exception {
    doTestNull(CharMatcher.any());
    doTestNull(CharMatcher.none());
    doTestNull(is('a'));
    doTestNull(isNot('a'));
    doTestNull(anyOf(""));
    doTestNull(anyOf("x"));