Author Topic: All about Regression Testing  (Read 161 times)

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Offline Transformer10

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All about Regression Testing
« on: October 14, 2008, 06:56:58 PM »
Regression testing is any type of software testing which seeks to uncover software regressions. Such regressions occur whenever software functionality that was previously working correctly stops working as intended. Typically regressions 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.
Regression test generation

Effective regression tests generate sufficient code execution coverage to exercise all meaningful code branches. Therefore, software testing is a combinatorial problem. However, in practice many combinations are unreachable so the problem size is greatly reduced. Every boolean decision statement requires at least two tests: one with an outcome of "true" and one with an outcome of "false". As a result, for every line of code written, programmers often need 3 to 5 lines of test code.[1]

Traditionally, in the corporate world, regression testing has been performed by a software quality assurance team after the development team has completed work. However, defects found at this stage are the most costly to fix. This problem is being addressed by the rise of developer testing. Although developers have always written test cases as part of the development cycle, these test cases have generally been either functional tests or unit tests that verify only intended outcomes. Developer testing compels a developer to focus on unit testing and to include both positive and negative test cases.[2]

When regression test generation is supported by a sustainable process for ensuring that test case failures are reviewed daily and addressed immediately, the end result is a regression test suite that evolves with the application, and becomes more robust and more intelligent each day. [3] If such a process is not implemented and ingrained into the team\'s workflow, the application may evolve out of sync with the generated test suite — increasing false positives and reducing the effectiveness of the test suite.


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.


    * "Also as a consequence of the introduction of new bugs, program maintenance requires far more system testing per statement written than any other programming. Theoretically, after each fix one must run the entire batch of test cases previously run against the system, to ensure that it has not been damaged in an obscure way. In practice, such regression testing must indeed approximate this theoretical idea, and it is very costly." -- Fred Brooks, The Mythical Man Month (p 122)

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All about Regression Testing
« on: October 14, 2008, 06:56:58 PM »

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