Major computer companies and government agencies are adopting Web Services (WS) technology. Web services must ensure interoperability and security, and be reliable and trustworthy. Consumers must make runtime decisions based on an intelligent and unbiased evaluation. We propose one component of a test suite generator to address this critical issue. The goal is to transform the labor-intensive software development process into a largely automated web services development process. The method operates within a service-oriented architecture, with the models and tools implemented as services that can be added, removed and replaced at runtime. We propose a generic greedy algorithm based on covering arrays for application in this environment. "Web services are not yet widely used because of security concerns. But there's an even bigger roadblock waiting just down the road - it's called trust. The big issue is "Will the service work correctly every time when I need it?" As yet few are thinking about the issues of testing and certification. We suggest that testing and certification of Web services is not business as usual and that new solutions are needed to provide assurance that services can really be trusted." (CBDi Forum, http://searchwebservices.techtarget.com, 11 July 2002).