Service Oriented Architecture (SOA) is changing the way in which software applications are designed, deployed and maintained. A service-oriented application consists of the runtime composition of autonomous services that are typically owned and controlled by different organizations. This decentralization impacts on the dependability of applications that consist of dynamic services agglomerates, and challenges their validation. Different techniques can be used or combined for the verification of dependability aspects, spanning over traditional off-line testing approaches up till monitoring and on-line testing. In this chapter we discuss issues and opportunities of SOA validation, identify three different stages for validation along the service life-cycle model, and overview some proposed research approaches and tools. The emphasis is on on-line testing, which to us is the most peculiar stage in the SOA validation process. Finally, we claim that on-line testing is only possible within an agreed governance framework.