What is Concurrency Testing?

Concurrency testing also known as the multi user testing is used to examine the defects in application when the same application is accessed by the multiple different users at the same time. Concurrency testing is used to measure the level of deadlocking, locking, semaphores.

In today’s internet world computer may be simultaneously serving thousands of clients with thousands of processors in execution.  In such situation computer may enter into the dead-lock state. To avoid this deadlock state concurrency testing is performed where multiple users request for the same application.


Concurrency testing helps in identifying the problems in system parameters such as response time, throughput or other issues related to the concurrency.  The performance is measured by adding the concurrent users using the Virtual User Generator (VUG). CHESS is an automated tool from Microsoft research which is used to find errors such as deadlocks.

The following shows how we carry out concurrent testing:

istqb definition of concurrency testing

First we need to examine the need of the concurrency testing. This is done by studying the design documents. Once the need is established we carry out the testing by designing the test cases. We start the testing manually by setting up the testing environment.

We make to seat two or more peoples in the adjacent seats and tell them to carry out the same task simultaneously. The output of the concurrency testing is either successful or failure. Defects are found if any by the people working together and doing the same task.

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