There are three different techniques for regression testing. They are discussed below.

Regression test selection technique: This technique attempts to reduce the time required to retest a modified program by selecting some subset of the existing test suite.

Test case prioritization technique: Regression test prioritization attempts to reorder a regression test suite so that those tests with the highest priority, according to some established criteria, are executed earlier in the regression testing process rather than those with lower priority. There are two two two types of prioritization:

General test case prioritization: For a given program $P,$ and test suite $T,$ we prioritize the test cases in $T,$ that will be useful over a succession of subsequent modified versions of $P,$ without any knowledge of the modified version.

Version-specific test case prioritization: We prioritize the test cases in $T,$ when $P,$ is modified to $P^{\prime}$ , with the knowledge of the changes made in $P .$

Test suite reduction technique: It reduces testing costs by permanently eliminating redundant test cases from test suites in terms of codes or functionalities exercised.