protected Pair<OAuth20AccessToken, OAuth20RefreshToken> assertRefreshTokenOk(final OAuthRegisteredService service) throws Throwable {
        val principal = createPrincipal();
        val refreshToken = addRefreshToken(principal, service);
        return assertRefreshTokenOk(service, refreshToken, principal);
    }
This is {@link AbstractOAuth20Tests}.

@author Misagh Moayyed
@since 5.0.0
support/cas-server-support-oauth/src/test/java/org/apereo/cas/AbstractOAuth20Tests.java