The software development process requires a huge amount of work. In fact, modifying or adding new features to any application can cause other elements that previously worked properly to fail or drop in functionality.
So, to make sure that development proceeds properly, developers must enlist the help of so-called regression test or regression testing. The corporate software development department very often has the need to have to change existing code, even if it is already tested and working, to integrate other features.
At this stage, the regression test has a vital task in that it makes sure that the changes inserted do not adversely affect the functioning of the already developed and tested app. Doing so will ensure that products are always of high quality and reliability. But how exactly does such a test work and what benefits does it have to offer?
What is a regression test and why is it important
Whenever software undergoes changes or updates, new bugs may unintentionally appear or old defects that have already been found may reappear. This may be due to the lack of established code-level review practices or because of previous version control systems that have led to a certain malfunction.
It also sometimes happens that the solution identified for a certain problem works only in a defined number of in-principle observed and expected cases, but not in a broader context of actual software use cases. If the program loses functionality as a result of updates, it is then said to be "regressed" to a less developed state, hence the expression regression test.
In summary, regression testing has the primary purpose of cushioning and minimizing this whole category of inconveniences, and although it can be programmed manually, to cut down on time and costs it has become the practice to perform it through special automated testing tool According to different techniques.
Some of these methodologies are based on retesting all test cases in the test group itself (retest all). Other systems, on the other hand, choose only a portion of them in a targeted form (regression test selection) or priority is given to test cases with a higher probability of finding bugs.
In any case, regardless of the technique chosen, regression tests can become wasteful in terms of resources expended and time, and are the responsibility of development teams who, even with knowledge of the most minimal code changes, will not be able to envision all the hypothetical cases and ways in which the software will actually be used.
At the same time, regression tests cannot be avoided because a poor quality app is abandoned very quickly by a fickle audience. Especially in work teams set up according to Agile and DevOps approach work cycles are split into shorter segments and code changes are more frequent. This requires that regression tests be performed without slowing down the rapid app deployment process.
The advantages of regression tests
Regression testing can ensure a great many benefits at every stage of the software development cycle. The most immediate benefit is that regression testing ensures that the application runs smoothly after code changes or additional features are added. However, there are other good reasons to perform this type of testing:
- Finding a potential system bug right away: One of the merits of regression testing is the almost immediate detection of bugs and glitches related to a new feature or code change. The ability to quickly unearth problems means that software can be fixed and returned promptly to users.
- Contain unnecessary expenses: regression testing helps to cut a number of costs related to the development area. In this way, long production downtimes can be avoided. In addition, less time and obviously money will be lost in implementing new features since their functionality can be quickly defined. Those with automated testing tools will also be able to save money on various development projects by reducing manual testing;
- Relying on continuous integration: automated testing tools gradually become more efficient during the development process as data from previous tests help add information to the testing process. This means that development departments can finally set up continuous integration. The release of new code can automatically trigger a series of tests from the regression test suite.
The techniques of regression testing
To conduct regression tests there are multiple techniques to use. Here are what are the most common methodologies used by IT departments today:
- Selection of regression tests: this method goes to analyze the changes made to the application code, but it will decide to run only specific tests in which the behavior of the software might have changed since the last code update. Since the system focuses only on a small part of the tests, it needs less time and is easier to integrate into the software development work;
- Retest everything: re-testing consists of rerunning all regression tests. In fact, all previous tests already performed are repeated again with the new coding and may reveal regressions related to the new addition to the code. This technique is used when the application has to undergo a large-scale change. Obviously, it is time-consuming, but it is good to be meticulous in cases of significant changes.
- Unit regression: unit regression is part of the regression tests in which the code is tested in isolation. It means that other interactions and dependencies are disabled during the execution of the test and the focus is on the single unit code. Typically, this test is performed during traffic-limited hours and not during peak hours.
The costs of regression tests
If one decides to perform the various regression tests manually, the cost may rise, and not just a little. So before relying on regression tests, it is always useful to inquire in advance about the expenses associated with them. Although this kind of testing can prove to be quite expensive, without regression tests there is a serious risk of not fully satisfying software users due to bugs or other problems.
Generally speaking, however, to evaluate the cost of regression testing, 3 elements must be considered primarily:
- Test time: the more time it takes the development team to perform the tests, the more expensive they will be. Even if you prefer automated testing, losing days of testing will still be more expensive than a test that needs only a few hours;
- Frequency of test execution: Obviously, the greater the number of tests, the more they will cost. Each test involves economic and time resources, draining the budget set aside for software development. Unfortunately, these tests must be carried out with some frequency, and in that detail lies the bulk of the expense;
- Software complexity: more complex software consequently needs more attention and more testing to ensure its smooth operation. So, the more articulated the software, the higher the expense.