Non-functional testing is the testing of a software application or system for its non-functional requirements: the way a system operates, rather than specific behaviours of that system. This is in contrast to functional testing, which tests against functional requirements that describe the functions of a system and its components. The names of many non-functional tests are often used interchangeably because of the overlap in scope between various non-functional requirements. For example, software performance is a broad term that includes many specific requirements like reliability and scalability.
Non-functional testing includes:
Endurance testing or reliability testing
Localization testing and Internationalization testing