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.