Functional requirements must be tested to check if the system executes as the end user expects. Validation environments must be able to test multiple kinds of applications that belong to different domains and technologies. Since this wide validation spectrum is very difficult to cope with, validation environments are usually specialized in domains, programming languages, technologies, etc. However, it is possible to identify that the validation processes for different systems share a set of commonalities and variability points. This is a perfect framework to apply the software product line approach to develop domain specific validation environments for testing specific products. In this paper we present our experience of applying software product lines to support the variability of validation environments. We illustrate our product-line experience of developing two domain-specific validation environments for two different case studies: digital TV and slots machines.