private static Authorizer<String> newMock() {
        @SuppressWarnings("unchecked")
        final Authorizer<String> mock = mock(Authorizer.class);
        lenient().when(mock.orElse(any())).thenCallRealMethod();
        return mock;
    }
When the first {@link Authorizer} returns a {@link CompletionStage} that fulfills with {@code null},
the second {@link Authorizer} shouldn't be invoked.
core/src/test/java/com/linecorp/armeria/server/auth/AuthorizerTest.java