System Testing -Types of testing

System testing is probably the most important phase of complete testing cycle. This phase is started after the completion of other phases like Unit, Component and Integration testing. During the System Testing phase, non functional testing also comes in to picture and performance, load, stress, scalability all these types of testing are performed in this phase.
By Definition, System Testing is conducted on the complete integrated system and on a replicated production environment. System Testing also evaluates that system compliance with specific functional and non functional requirements both.
It is very important to understand that not many test cases are written for the system testing. Test cases for the system testing are derived from the architecture/design of the system, from input of the end user and by user stories. It does not make sense to exercise extensive testing in the System Testing phase, as most of the functional defects should have been caught and corrected during earlier testing phase.

Utmost care is exercised for the defects uncovered during System Testing phase and proper impact analysis should be done before fixing the defect. Some times, if business permits defects are just documented and mentioned as the known limitation instead of fixing it.

Progress of the System Testing also instills and build confidence in the product teams as this is the first phase in which product is tested with production environment.

System Testing phase also prepares team for more user centric testing i.e User Acceptance Testing.
Entry Criteria
* Unit, component and Integration test are complete
* Defects identified during these test phases are resolved and closed by QE team
* Teams have sufficient tools and resources to mimic the production environment
* Teams have sufficient tools and resources to mimic the production environment

Exit Criteria
* Test cases execution reports shows that functional and non functional requirements are met.
* Defects found during the System Testing are either fixed after doing thorough impact analysis or are documented as known limitations.