@Test
    void verifyMissingIssuer() throws Throwable {
        val claims = new JwtClaims();
        claims.setIssuer("unknown");
        val token = claims.toJson();
        assertNull(accountRegistrationService.validateToken(token));
    }
This is {@link DefaultAccountRegistrationServiceTests}.

@author Misagh Moayyed
@since 6.5.0
support/cas-server-support-account-mgmt/src/test/java/org/apereo/cas/acct/DefaultAccountRegistrationServiceTests.java