Regression Testing

Regression Testing
Common methods of regression testing include re-running previously run tests and checking whether previously fixed faults have re-emerged. Although this may be done through manual testing procedures using programming techniques, it is often done using automated testing tools. Such a 'test suite' contains software tools that allow the testing environment to execute all the regression test cases automatically; some projects even set up automated systems to automatically re-run all regression tests at specified intervals and report any regressions.
Types of regression
Local - changes introduce new bugs.
Unmasked - changes unmask previously existing bugs.
Remote - Changing one part breaks another part of the program. For example, Module A writes to a database. Module B reads from the database. If changes to what Module A writes to the database break Module B, it is remote regression.
There's another way to classify regression.
New feature regression - changes to code that is new to release 1.1 break other code that is new to release 1.1.
Existing feature regression - changes to code that is new to release 1.1 break code that existed in release 1.0.