Smoke Testing is also called Build Verification Testing or Rattle Testing or Confidence Testing is done to validate code changes before the changes are checked in into the product’s official source code.After receiving a software build, with minor changes in code, or functionality, Sanity testing is performed to ascertain that the bugs have been fixed and no further issues are introduced due to these changes if this basic functionality itself is not working then there is no meaning in testing of the other functionalities in that project.For Example a typical smoke test would be - Verify that the application launches successfully, Check that the GUI is responsive ... etc.

This can be done either by developers or testers. If developers do this, it should be done before the release of product (or “build”) and if testers, - done before moving to next types of testing. Nowadays these tests are performed by some automated system which is included in the build mechanism.

• Smoke testing originated in the hardware testing practice of turning on a      new  piece of hardware for the first time and considering it a success if it does not catch fire and smoke. In software industry, smoke testing is a shallow and wide approach whereby all areas of the application without getting into too deep, is tested.
•  A smoke test is scripted, either using a written set of tests or an automated test
• A Smoke test is designed to touch every part of the application in a cursory way. It’s shallow and wide.
• Smoke testing is conducted to ensure whether the most crucial functions of a program are working, but not bothering with finer details. (Such as build verification).
• Smoke testing is normal health check up to a build of an application before      taking it to testing in depth.

 Sanity Testing

• Sanity testing, this is also called tester Acceptance testing. This is to determine, whether the supplied build is testable or not. In other words Sanity testing is testing the application to ensure, if it is stable enough to continue further testing. If the test fails, we cannot continue testing further. Sanity testing is the initial test after the build release. It is done by the QA team.
• 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.