Performance testing technology employs one or more PCs to act as injectors - each emulating the presence or numbers of users and each running an automated sequence of interactions (recorded as a script, or as a series of scripts to emulate different types of user interaction) with the host whose performance is being tested. Usually, a separate PC acts as a test conductor, coordinating and gathering metrics from each of the injectors and collating performance data for reporting purposes. The usual sequence is to ramp up the load - starting with a small number of virtual users and increasing the number over a period to some maximum. The test result shows how the performance varies with the load, given as number of users vs response time. Various tools, including Compuware Corporation's QACenter Performance Edition, are available to perform such tests. Tools in this category usually execute a suite of tests which will emulate real users against the system. Sometimes the results can reveal oddities, e.g., that while the average response time might be acceptable, there are outliers of a few key transactions that take considerably longer to complete - something that might be caused by inefficient database queries, etc.
Performance testing can be combined with stress testing, in order to see what happens when an acceptable load is exceeded -does the system crash? How long does it take to recover if a large load is reduced? Does it fail in a way that causes collateral damage?
performance testing tool
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