PROSA is an online testing and failure prediction framework that uses both monitoring and online testing of services to more accurately predict failures compared to only using monitoring. It triggers tests of services based on usage rates and uses the results along with monitoring data as input to prediction models. Experiments show that online testing improves prediction accuracy over only monitoring, and that factors like higher usage rates, online test rates, and certain prediction models lead to greater accuracy gains. The goal is to anticipate failures to allow for proactive repair or mitigation actions.