Sanity testing
A sanity test is a narrow regression test that focuses on one or a few areas of functionality. Sanity testing is usually narrow and deep. A sanity test is usually unscripted. A Sanity test is used to determine a small section of the application is still working after a minor change. Sanity testing is a cursory testing; it is performed whenever a cursory testing is sufficient to prove the application is functioning according to specifications. This level of testing is a subset of regression testing. Sanity testing is to verify whether requirements are met or not, checking all features breadth-first.
Sanity testing is also similar to Smoke testing, but has some minor differences. Sanity testing is done when the application is deployed into testing for the very first time and in smoke testing only positive scenarios are validated but in sanity testing both the positive and negative scenarios are validated.