Types Of Testing

ü  Performance Testing – Performance tests are used to evaluate and understand the application’s scalability when, for example, more users are added or the volume of data increases. This is particularly important for identifying bottlenecks in high usage applications. The basic approach is to collect timings of the critical business processes while the test system is under a very low load (a ‘quiet box’ condition) and then collect the same timings with progressively higher loads until the maximum required load is reached. For a data retrieval application, reviewing the performance pattern may show that a change needs to be made in a stored SQL procedure or that an index should be added to the database design.

ü  Stress Testing – Stress Testing is performance testing at higher than normal simulated loads. Stressing runs the system or application beyond the limits of its specified requirements to determine the load under which it fails and how it fails. A gradual performance slow-down leading to a non-catastrophic system halt is the desired result, but if the system will suddenly crash and burn it’s important to know the point where that will happen. Catastrophic failure in production means beepers going off, people coming in after hours, system restarts, frayed tempers, and possible financial losses. This test is arguably the most important test for mission-critical systems.

ü  Load Testing – Load tests are the opposite of stress tests. They test the capability of the application to function properly under expected normal production conditions and measure the response times for critical transactions or processes to determine if they are within limits specified in the business requirements and design documents or that they meet Service Level Agreements. For database applications, load testing must be executed on a current production-size database. If some database tables are forecast to grow much larger in the foreseeable future then serious consideration should be given to testing against a database of the projected size.

Performance, stress, and load testing are all major undertakings and will require substantial input from the business sponsors and IT staff in setting up a test environment and designing test cases that can be accurately executed. Because of this, these tests are sometimes delayed and made part of the User Acceptance Testing phase. Load tests especially must be documented in detail so that the tests are repeatable in case they need to be executed several times to ensure that new releases or changes in database size do not push response times beyond prescribed requirements and Service Level Agreements.