Quality management for Web services

Computerworld - Web services provide organizations with flexible, standards-based mechanisms for deploying business logic and functionality to distributed consumers. When functionality is distributed, however, quality management becomes imperative.
Mission-critical functions and sensitive data handling must work quickly and accurately at all times. To ensure this level of quality, organizations must employ test processes to ensure that the Web services are developed and deployed to meet these standards.
Defining the service
Quality starts with requirements. In order to design and deliver Web services, developers must know what functionality is needed. The more specific the requirements, the better the development effort. "The Web service must be fast" is a useless requirement. "The Web service must provide accurate responses in under two seconds on a 24/7 basis with up to 500 concurrent users" is better because having measurable requirements allows developers to work toward a goal. Defining boundaries like "up to 500 users" gives the project scope. Without these boundaries, code is likely to be developed inefficiently.
Likewise, testers must know what functional and performance requirements have been defined. Developers work on interpreting user requirements to generate code. Test strategy should be done concurrently to ensure that testers work from the same requirements used by development. If test strategy is based on developed code as opposed to initial requirements, the resulting end product may be based on a single individual's misinterpretation of a requirement.
By creating tests based on the original requirement documents, additional people interpret the project needs. That said, if differences in requirement interpretation arise, resolution early in the process occurs as opposed to discovery after development is complete. In this example, the testing group acts as an early check and balance on the software development process.
Once service-level agreements (SLA) are established, both parties (provider and consumer) need to agree on what measurements to take, what metrics to report, the success criteria and the ramifications should the provider fail to deliver. Following deployment of the Web services, both parties have a vested interest in monitoring the delivery of functionality. Web service testing and monitoring must cover the agreed upon metrics including the following:

• Availability: must be running and reachable


• Performance: must respond to requests within acceptable time limits


• Accuracy: must be accurate regardless of load


• Standards compliance: must work with all potential client types


• Integration: must work with all services and applications within the enterprise