Regression testing Introduction

Regression testing is any type of software testing which seeks to uncover regression bugs. Regression bugs occur whenever software functionality that previously worked as desired, stops working or no longer works in the same way that was previously planned. Typically regression bugs occur as an unintended consequence of program changes.

Common methods of regression testing include re-running previously run tests and checking whether previously fixed faults have re-emerged.

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.

Uses of Regression Testing

Regression testing can be used not only for testing the correctness of a program, but it is also often used to track the quality of its output. For instance in the design of a compiler, regression testing should track the code size, simulation time and compilation time of the test suite cases.

Recommended Resources
• Testing Interview Questions - http://www.coolinterview.com/type.asp
• Testing Tools Interview Questions - http://www.coolinterview.com/type.asp
• What is Software Testing?- http://en.wikipedia.org/wiki/Software_testing
• Software QA & Testing Resource Center- http://www.softwareqatest.com/
• Testing Faqs- http://www.testingfaqs.org/