There are two kinds of change. There’s the kind that moves things forward and the kind that moves things backward. The latter is called regression, and it is more often than not the opposite of what we are trying to achieve. When a software developer sits down to try and move an element of their product forward, the last thing they want is to accidentally move another aspect backward in the process.
This is not an unreasonable concern. Apple faced lawsuits for throttling older iPhones through software updates, and after waiting in online queues all night, the first PlayStation 5 owners were disappointed to find that putting their console in rest mode resulted in data losses, freezing, and corrupted crashes.
Enter: the solution.
What is Regression Testing?
Regression testing is a type of software testing that protects the integrity of a software’s existing features by ensuring that they weren’t compromised by recent code changes.
Think of it like this: you have a learning management software that needs to be updated to allow instructors to leave 1000 words of feedback instead of the former 500 limit.
However, when a tester tries to exercise the new 1000-limit, not only does the dreaded “over 500” alert still appear in the corner of the screen. The cursor stalls and does not let the tester proceed typing at all. The tester can reasonably include, then, that an error had occurred at some point during the upgrade.
Put simply, regression testing is about making sure new features don’t destroy old features that weren’t meant to be changed.
Regression Testing vs. User Acceptance Testing (UAT)
Regression testing is not part of user acceptance testing. Rather, user acceptance testing is the last type of testing performed before the software is made available to the public. In this process, beta users test the software to ensure complete user satisfaction upon release.
They both ensure the quality of the software, but the difference is that UAT is conducted by real clients. Regression testing is not conducted by users, it’s performed manually by quality assurance professionals or developers and is often executed automatically.
Regression testing is performed before user acceptance testing to fix bugs and make necessary changes, and then UAT occurs to determine whether the performance as a whole is satisfactory.
Regression Testing vs. Unit Testing vs. Integration Testing
Unit testing is the process of testing a small piece of code and ensuring that it is functioning as it should. Integration testing illustrates the way that different elements of the software work together. Regression testing is, essentially, re-running defined unit and integration tests focused on the parts of the software that should function the same as before.
How Is Regression Testing Performed?
The process can’t begin until the code is debugged. Once the bugs have been exposed, necessary changes can be made to fix them. This can be accomplished through a couple of different approaches.
- Manual: Manual regression testing can be effective for smaller, more manageable projects. Initially, you’ll have to decide whether you’re going to test the entire suite or only affected areas (more detail on that below). The process involves identifying updates made, problems caused by those updates, and inputting relevant cases into a test management software. Then, you’ll have to make bug reports and confirm test coverage.
- Automated: Automated regression testing is the standard for larger, more time-consuming projects. Usually, this kind of testing is implemented after the software is stable, meaning without any expected critical changes. Automation is extremely beneficial in detecting bugs that appear randomly.
Regression testing is a kind of art. Like any art, there are different techniques that one can utilize to achieve the desired result. In regression testing, those techniques are:
- Retest All: This technique requires checking the integrity of a program by re-running all of the cases. It is the most expensive option by far, but ensures there are no errors.
- Regression test selection: Instead of running all cases, this technique runs part of the test suite.
- Test Case Prioritization: This technique executes high priority test cases before low priority ones.
- Hybrid: A combination of the latter two techniques.
Now that you have all of the information, you’re ready for the step-by-step.
Step 1: Build A Test Suite
You can create your test suite from existing test cases or from scratch. Either way, you’re selecting test scenarios that you want to run through. As the software grows, more and more test cases are added, which is why automation is an inevitable part of the process.
Step 2: Choose An Approach
As previously mentioned, this is going to depend on several factors. Ideally, you’ll strike a balance between manual and automated testing.
Step 3: Choose Your Cases
There are a few elements to consider when selecting cases. Does it cover a core function of your software? Does it cover new features (which are more fragile)? Has it been defective before? Once you have weighed these aspects, you can schedule your tests.
Step 4: Determine Frequency
There’s a simple rule to follow here: when a change is made, run tests. Regression testing should be performed every time changes are made to ensure that the functionality of the software remains intact. If your software is large enough, this might only be attainable through automated regression testing.
What Makes A Perfect Regression Test?
The test suite is where all the magic happens. Your test suite should be focused on parts of the software that have undergone recent change and the nearby areas. Cases that highlight both the modified and affected parts of the code are essential.
Ideally, you will select test cases with frequent defects, visible functionality, and verification of core features. You also need all integration and complex test cases as well as samples of successful and failed cases.
What Are The Challenges Of Regression Testing?
Like many things, many of the challenges of regression testing come in having a lack of resources. The larger the project and the more complex the code, the more resources are needed to run regular tests. Regular tests are necessary to maintain the integrity of the software, which means that the determination of just how frequent changes are made depending on resources is a constant challenge.
The process of conducting regression testing is intensive. Compiling a test suite that includes cases that highlight the most important parts of the code, choosing an approach, deciding what to automate, and integrating regular regression tests into the overall testing process.
In short, it’s time consuming.
It can also be difficult to sell the importance of regression testing to non-technical members of the company. Executives are focused on the continued growth of the product, and convincing them to invest a significant amount of time and money into regression testing can be a challenge. In this case, communicating the importance of the process is vital.
Regression testing means preserving and maintaining the functionality of a software. Without it, programs would be riddled with bugs produced by last-minute tweaks that significantly impact the user experience. If you are building a software, you’re investing a significant amount of time, money, and energy into the process. Regression testing is the way to ensure all of that work is not in vain. It protects the integrity of your project and confirms that your vision is delivered to the world as accurately as possible.