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Q&A: Can your application handle the load?

Enterprise applications, by their very nature, are used by people in many different locations. That being the case, testing an enterprise app's functionality is only part of the job. An enterprise application must also be able to handle a variety of loads while continuing to function flawlessly.

With that in mind, we recently spoke to Jim Floyd, Compuware's QACenter Performance Edition product manager. Jim joined Compuware in 1994 and has specialized in automated testing for the past nine years.

Q: What are some of the most common mistakes that testers make when load testing an application?

A: Many testers feel that any performance test will identify performance problems. Consequently, they focus more on the test event and not on what should go into the test. What they need to do is to gather more pertinent information about how the application will run, including traffic levels, use levels, error rates and response times. This information will let them properly set expectations and success requirements.

Q: How does load testing of Web applications differ from load testing of client/server applications?

A: Although Web applications tend to pull together many more diverse back-end systems, scripting for Web applications tends to be much easier than scripting for client/server apps. When writing test scripts for client/server applications, test engineers must write scripts that use low-level protocols to replicate the traffic between client and server.

Q: Is there anything out there that is not currently an issue for load testing, but could become an issue in the future?

A: As security systems get better at preventing attacks like denial of service (DoS) or other types of traffic flood attacks, generating the load is becoming harder. The reason for this is that the new security systems now use sophisticated algorithms to validate the authenticity of the traffic flowing through the systems. The problems that load testers will face in the future are how to differentiate the load generated by a legitimate load tool from the one used during a DoS attack, and how to ensure that the applications and security systems under test will react properly to legitimate load and prevent DoS attacks.

Q: Compuware's QACenter Performance Edition now has a licensing structure that's a little different. Can you describe it?

A: Historically, load-testing solutions charge by the project, forcing a customer to purchase a set of virtual users for each project/department using them. The load-testing tools are priced by virtual users, meaning that if a customer has two or more projects or departments wishing to use the tool, they will end up paying for two or more virtual user licenses, which increases the Total Cost of Ownership.


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About the Author

Dan Romanchik is an engineering manager turned writer and Web developer. His current passion is amateur radio. You can read his amateur radio blog at www.blurty.com/~kb6nu.

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