*       {@code cls}, instance methods are skipped for nulls test.
   *   <li>Nulls test is not performed on method return values unless the method is a non-private
   *       static factory method whose return type is {@code cls} or {@code cls}'s subtype.
   * </ul>
   */
  public void testNulls(Class<?> cls) {
    try {
      doTestNulls(cls, Visibility.PACKAGE);
    } catch (Exception e) {

    TreeMap<String, Class<?>> classMap = Maps.newTreeMap();
    for (Class<?> cls : classes) {
      classMap.put(cls.getName(), cls);
    }
    // Foo.class -> [FooTest.class, FooTests.class, FooTestSuite.class, ...]
    Multimap<Class<?>, Class<?>> testClasses = HashMultimap.create();
    LinkedHashSet<Class<?>> candidateClasses = new LinkedHashSet<>();
    for (Class<?> cls : classes) {
      String testedClassName = TEST_SUFFIX.chop(cls.getName());

    TreeMap<String, Class<?>> classMap = Maps.newTreeMap();
    for (Class<?> cls : classes) {
      classMap.put(cls.getName(), cls);
    }
    // Foo.class -> [FooTest.class, FooTests.class, FooTestSuite.class, ...]
    Multimap<Class<?>, Class<?>> testClasses = HashMultimap.create();
    LinkedHashSet<Class<?>> candidateClasses = new LinkedHashSet<>();
    for (Class<?> cls : classes) {
      String testedClassName = TEST_SUFFIX.chop(cls.getName());

        Charset charset,
        TimeUnit unit,
        Class<?> cls,
        Joiner joiner,
        Pattern pattern,
        UnsignedInteger ui,
        UnsignedLong ul,
        StringBuilder sb,
        Predicate<?> pred,
        Function<?, ?> func,
        Object obj) {
      delegate.foo(
          s, r, n, it, b, eq, e, in, c, ord, charset, unit, cls, joiner, pattern, ui, ul, sb, pred,
          func, obj);
    }

        Charset charset,
        TimeUnit unit,
        Class<?> cls,
        Joiner joiner,
        Pattern pattern,
        UnsignedInteger ui,
        UnsignedLong ul,
        StringBuilder sb,
        Predicate<?> pred,
        Function<?, ?> func,
        Object obj) {
      delegate.foo(
          s, r, n, it, b, eq, e, in, c, ord, charset, unit, cls, joiner, pattern, ui, ul, sb, pred,
          func, obj);
    }

                Middleware(AsyncExitStackMiddleware),  # ty: ignore[invalid-argument-type]
            ]
        )

        app = self.router
        for cls, args, kwargs in reversed(middleware):
            app = cls(app, *args, **kwargs)
        return app

    def openapi(self) -> dict[str, Any]:
        """
        Generate the OpenAPI schema of the application. This is called by FastAPI