Conformance testing is a crucial phase in the life-cycle of communicating systems. However, classical testing methods are not appropriate for use in all tasks concerning the test of telecommunications services (especially regression and integration tests). This is so because Intelligent Networks, into which these services are installed, are modular architectures (composed of building blocks) evolving basically by the addition of new services/features that may share the same resources (reusability). This paper investigates how embedded conformance testing methods can be applied in the context of service validation, taking into account the different testing phases in the service life-cycle. In order to illustrate their application, the validation of telephone services (Basic Call Service, Originating Call Screening and Call Forward Unconditional) on an Intelligent Network framework is presented. It is also shown how some cases of feature interaction can be detected.