Development of a software system from existing components can surely have various benefits, but can also entail a series of problems. One type of problems is caused by a limited exchange of information between the developer and user of a component. A limited exchange and thereby a lack of information can have various consequences, among them the requirement to test a component prior to its integration into a software system. A lack of information cannot only make test prior to integration necessary, it can also complicate this tasks. However, difficulties in testing can be avoided if certain provisions to increase testability are taken beforehand. This article describes a new form of improving testability of, particularly commercial, components, the self-testing COTS components (STECC) strategy.