A Quality Assurance process often involves a phase called exploratory testing, and it involves a tester or QA engineer, typically asserting the quality of a user interface, trying it out in various ways, looking for problems. Exploratory testing is characterized by the relatively small amount of planning. When the QA engineer is shown a graphical representation of the behaviour (the statechart) of the system under test, it functions as a map of the behaviour; a map that can be traversed. Any state in such a statechart should be accessible, and the tester can understand from the statechart how to arrive at various states.
- The statechart can be inspected to see if there are several paths to arrive at a state; these should be possible to test
- The tester can check that all states and all transitions have been explored
- Statecharts makes it easy to write unit tests that can verify behavioural aspects.
NASA's JPL says that "test engineers were very happy to have [visual statecharts]", and that when writing unit tests, the developer used "a red marker and checked off every state in every transition".