There are some aspects which are complex such as Performance of an application etc and this testing checks the Quality of the software to be tested. Quality majorly depends on Time, Accuracy, Stability, correctness and durability of a product under various adverse circumstances.
In software terms, when an application works as per the user’s expectation, smoothly and efficiently under any condition, then it is stated as a reliable application. Based on these aspects of quality, it is very critical to test under these parameters. This type of testing is called Non- Functional Testing.
It is not feasible to test this type manually, hence some special automated tools are used to test it.