@Test
    void verifyBadSecret() throws Throwable {
        val service = addRegisteredService(SERVICE_URL, UUID.randomUUID().toString());
        val auth = service.getClientId() + ':' + CLIENT_SECRET;
        val body = (OAuth20IntrospectionAccessTokenFailureResponse) internalVerifyOperation(auth, service);
        assertNotNull(body.getError());
    }
This is {@link OAuth20IntrospectionEndpointControllerTests}.

@author Misagh Moayyed
@since 6.1.0
support/cas-server-support-oauth/src/test/java/org/apereo/cas/support/oauth/web/endpoints/OAuth20IntrospectionEndpointControllerTests.java