The process of testing changes to computer programs and ensuring that the older programming works with the new change is known as Regression Testing. Performed by experienced code testing specialists, regression testing is a part of the program development process in which code test cases are designed to test new code units. This type of testing is done to ensure that changing or adding new codes to a particular program does not lead to errors into the codes which are not intended to be impacted.
Also known as verification testing, regression testing is usually initiated once a programmer has added a source code program which might have introduced unintentional errors or after he/she has made an attempt to fix a recognized problem. Although this type of software testing can be done at all testing levels which include unit, integration, acceptance, but it is more relevant when executed at the system testing level.
A program or software has to undergo regression test but, in case there is a time or resource constraint, an impact analysis of the changes should be performed. This should focus on identifying the areas which can be highly influenced by the change and which can impact the user-experience in case of malfunction.
When is Regression Testing Necessary
- When there is change in requirements and the code is modified as per those changed requirements
- Anytime when a new feature is added or the software is upgraded
- To fix defects and performance issues, if any
Regression Testing Tools
Regression testing includes re-running the previous tests and comparing the results of these tests with those conducted earlier. A regression tester can develop regression test libraries from existing test cases that are being developed from day one. This implies that regression test cases need not be specifically written and anything that has been verified successfully throughout the development process, such as functional, unit, integration or the build verification tests, can all be easily incorporated into a regression test suite.
Modern methods of regression testing include employment of specialized commercial and automated testing tools. These capture snapshots that are compared with the results after applying a change because the number of functions and processes that a tester attempts to check through the regression testing process can be in thousands. Some of the automated tools for successfully running regression tests are:
- Regression Tester
- Rational Functional Tester
Points of Consideration while Conducting Regression Tests
The biggest advantage of regression testing process is that each time one modifies the source code, they can simply re-run the relevant tests to ensure that the test cases are completed without any errors. However, while running regression tests, it is critically important for the testers to keep in mind that even the smallest and insignificant of alterations to the source code can surprisingly break functions which are totally unrelated to the new modifications. Other points that one should also keep in mind are:
- The regression test suite should define highly visible functionality with succinct steps for successful execution of the test cases.
- The test suite should also include testing areas where the development did not make any changes whatsoever in a module’s code.
- Regression bugs should be logged, tracked, and documented accurately as this will be helpful in resolving them quickly.
- A regression test case should be updated or changed after every release.
The Process of Regression Testing
Regression tests are conducted not only to make sure that the modifications in the source code behave as expected, but also to ensure that there are no problems in functions which were behaving correctly when tested previously. To extract the most out of the regression testing method, one needs to follow these below-mentioned steps:
Creating a Plan:
Post the testing and debugging of the software and adding new features, a test plan is created by identifying key focus areas, strategies, and test entry and exit criterion. One can also outline testing pre-requisites and responsibilities in this step.
Creating Test Cases:
The second step is to create test cases which cover all the key focus areas and test the added features in the software. It also marks the description of what to test, the steps that ought to be followed, and the inputs and expected outputs. All the test cases should cover the functionality that the changes need to address and the components which may be affected by change.
Running the Test Cases:
Both the old and new tests are run over the new build.
In this step, the defects are tracked systematically and are fixed and re-run until all the test cases are error-free.
To conclude, a system must undergo the process of regression testing to ensure that there are no defects, even when the changes are done in the older codes. This method of software testing is also helpful in saving time and cost related to effecting the fix at a later stage.