Sanity testing is used to test that our application or major functionality is reasonably fit or working fine. It is performed when developers wants to know the quick status of the product after doing changes in the code to fix the previous reported bugs. It is done to avoid regression testing. It avoids the wasting of time & cost involved in regression testing if the build is failed. The procedures for both sanity testing & regression testing are almost same so we can categorize the sanity testing under regression testing.
Selection of Test cases for Sanity:-
The purpose of Sanity is only to test minimum number of test cases which covered the whole module.
It can't be depend on Regression test cases.
It also includes those test cases which comes under the important portion of module where severity of bugs can be high.