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What's Load Testing

Software Testing Methodolog

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What's Load Testing

The process of modeling application usage conditions and performing them against the application and system under test, to analyze the application and system and determine capacity, throughout speed, transation handling capabilities, scalabilities and reliability while under under stress.

This tyoe of test is designed to identify possible overloads to the system such as too many users signed on to the system, too many terminals on the network, and network system too slow.

Load testing a simulation of how a browser will respond to intense use by many individuals. The Web sessions can be recorded live and set up so that the test can be run during peak times and also during slow times. The following are two different types of load tests:

Single session - A single session should be set up on browser that will have one or multiple responses. The timeing of the data should be put in a file. After the test, you can set up a separate file for report analysis.

Multiple session - a multiple session should be developed on multiple browsers with one or multiple responses. The multivariate statistical methods may be needed for a complex but general performance model

When performing stress testing, looping transactions back on themselves so that the system stresses itself simulates stress loads and may be useful for finding synchronization problems and timing bugs, Web priority problems, memory bugs, and Windows problems using API. For example, you may want ot simulate an incoming message that is then put out on a looped-back line; this in turn will generate another incoming message. The nyou can use another system of comparable size to create the stress load.

Memory leaks are often found under stress testing. A memory leak occurs when a test leaves allocated memory behind and does not correctly return the memory to the memory allocation scheme. The test seems to run correctly, but after several iteration available memory is reduced until the system fails.

Peak Load and Testing Parameters:

Determining your peak load is important before beginning the assessment of the Web site test. It may mean more than just using user requests per second to stress the system. There should be a combination of determinants such as requests per second , processor time, and memory usage. There is also the consideration of the type of information that is on your Web page from graphics and code processing, such as scripts, to ASP pages. Then it is important to determine what is fast and what is slow for your system. The type of connection can be a critical component here, such as T1 or T3 versus a modem hookup. After you have selected your threshold, you can stress your system to additional limits.

As a tester you need to set up test parameters to make sure you can log the number of users coming into and leaving the test. This should be started in a small way and steadily increased. The test should also begin by selecting a test page that may not have a large amount of graphics and steadily increasing the complexity of the test by increasing the number of graphics and image requests. Keep in mind that images will take up additional bandwidth and resources on the server but do not really have a large impact on the server's processor.

Another important item to remember is that you need to account for the length of time the user will spend surfing each page. As you test, you should set up a log to determine the approximate time spend on each page, whether it is 25 or 30 seconds. It may be recorded that each user spends at least 30 seconds on each page, and that will produce a heightened response for the server. As the request is queued, and this will be analyzed as the test continues.

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