Regression testing、Smoke Test、Sanity testing

Regression testing is verifing that previously passed tests arestill OK after any change to the software or the environment, usually toverify that a change in one area doesn't affect other or unrelatedareas. Retesting? just running the same tests and conditions over andover again, to verify reproducability (precision)

Smoke Test:
When a build is received, a smoke test is run to ascertain if the build is stable and it can be considered for further testing.

Smoke testing can be done for testing the stability of any interim build.

Smoke testing can be executed for platform qualification tests.

Sanity testing:
Once a new build is obtained with minor revisions, instead of doing athrough regression, a sanity is performed so as to ascertain the buildhas indeed rectified the issues and no further issue has been introducedby the fixes.   Its generally a subset of regression testing and agroup of test cases are executed that are related with the changes madeto the app.

Generally, when multiple cycles of testing are executed, sanity testingmay be done during the later cycles after through regression cycles.

Smoke testing
1.Smoke testing originated in the hardware testing practice of turningon a new piece of hardware for the first time and considering it asuccess if it does not catch fire and smoke.   In software industry,smoke testing is a shallow and wide approach whereby all areas of theapplication without getting into too deep, is tested.  

2.A smoke test is scripted--either using a written set of tests or an automated test.

3.A Smoke test is designed to touch every part of the application in a cursory way. It's is shallow and wide.

4.Smoke testing will be conducted to ensure whether the most crucialfunctions of a program work, but not bothering with finer details. (Suchas build verification).

5.Smoke testing is normal health check up to a build of an application before taking it to testing in depth.

sanity testing
1. A sanity test is a narrow regression test that focuses on one or afew areas of functionality. Sanity testing is usually narrow and deep.

2.A sanity test is usually unscripted.

3.A Sanity test is used to determine a small section of the application is still working after a minor change.

4. Sanity testing is a cursory testing; it is performed whenever acursory testing is sufficient to prove the application is functioningaccording to specifications. This level of testing is a subset ofregression testing.

5.sanity testing is to verify whether requirements are met or not,
checking all features breadth-first.