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Thursday, August 23, 2007

Some definitions of regression testing and what it means ..

What is regression testing?

Regression is a type of software testing that is used for discovering new errors and bugs in the software system. In terminology of regression testing these bugs are called regressions. Regression testing is carried out for the already existing areas of the system whether functional or non – functional. This testing is carried out after any change has been made in the configurations or patches. The basic purpose of regression testing is ensuring that any change or modification made to the software does not affect its functionality or introduce some other new errors. It also checks whether a change in one part of the system had any effect on the other parts of the system. Some common methods of carrying out regressing testing are:

- Re – executing the tests that have already been executed.
- Checking if any change has occurred in the working of the software.
- Checking if the errors corrected earlier have appeared.

Regression testing as such is very time consuming since you have to test everything again and again, but can be performed effectively by selecting a certain number of tests. The number of tests selected is sufficient enough to cover the whole unit in which the change is made. According to a research, it has been found that making a change in one part of the software often introduces errors in other parts. In some of the cases the same errors reoccur because the fix that was made earlier to prevent them gets lost. This happens probably because of errors humans make while revising the code i.e., because of the poor revision practices. Often the fix that we apply for a problem is fragile that it is easily breakable and can get lost. Or sometimes this fix for one part of the software can cause an error in another part.
In some other cases it might happen that during redesigning, the same mistakes might be made that were made during the designing of the original software. Therefore mostly regression testing is considered to be a good practice. It helps in locating and fixing the bug, recording the tests which led to the discovery of the bugs, repeated execution of the tests at regular intervals after some modification has been done in the program. You might be thinking that this can be done even by following the manual testing procedure by means of some programming techniques. But this is better carried out with automated testing as it takes less effort and time when compared to the manual testing.
An automated testing suite consists of various software tools that allow for the automatic execution of the test cases and generate reports. The programmers might set up such automated testing systems for automatically doing regression testing at regular intervals of time. This way the regression tests can be run either after every compilation, once a week or even every night. There are various tools available for automated regression testing such as follows:
- TinderBox
- BuildBot
- Hudson
- Jenkins
- Bamboo
- TeamCity

Regression testing is closely associated with extreme programming as the former is an inseparable part of the latter. Here at each phase of the software development cycle, the entire software package is put through repeatable, extensive automated testing. The software quality assurance team is responsible for performing the regression testing after the development is over. But fixing the bugs at this stage comes very expensive. This potential problem is fixed at an earlier stage by means of unit testing. The test cases written by the programmers are for the verification of the intended outcomes i.e., they are either unit tests or functional tests. 

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