# Automated regression testing: A complete introduction Regression testing is a specific form of testing that verifies whether a given piece of software suffered regressions after undergoing changes. By Testim, March 26, 2026 ### Share on Regression testing is a specific form of testing that verifies whether a given piece of software suffered regressions after undergoing changes. “Regression” here means “going back to a previous undesired state.” So automated regression testing is nothing more than the process of automatically verifying that the application has not regressed to a previous undesired state. Ideally, regression testing—whether automated or not—is something you do every time a software application is changed in some way, whether by receiving a new feature, an improvement, or a bug fix. In today’s post, we’ll define and explain what automated regression testing means. We’ll start by explaining what a regression is, how costly they are for software teams, and why you should employ regression testing to avoid them. Since manual regression testing would be both time-consuming and error-prone, we’ll then proceed to cover the need for automation, offering advice and tips on how to actually implement the technique for your teams. Let’s get started! ## What Is Automated Regression Testing? Before we dive into the “how” of automated regression testing, we need to clarify its “what” and “why.” What _is_ it, after all? What does automated regression testing mean, and why should we use it? Automated regression testing is a form of automated testing meant to detect regressions in an application. “Regression”, in this context, means that the application has regressed back to an undesired state. For instance, an old bug resurfaced, or a previously perfect feature stopped working. ### Why Do We Need Regression Testing? As we’ve just defined in the previous section, “regression” means an unintentional reversion to a previous state. However, something really important was left implicit in the definition: software regression, more often than not, means the application went back to a _bad_ previous state. ### Regression Testing Is Vital in Software The field of software development is disproportionately prone to regression problems. Each addition or change made by any developer has the potential to cause unexpected problems in areas (supposedly) unrelated to the spot where it was performed. Regression testing is nothing more than the execution (partial or total) of a test suite in order to verify that a given application hasn’t returned to a previous undesired state. Developers should always keep in mind that all the changes they make, no matter how small, simple, or insignificant they seem, have the potential to cause surprising side effects. By performing regression tests, the developer checks that not only does their change behave as it’s supposed to, but also that it plays well with all of the code that was written up until that point. That’s where regression testing comes in handy. If manually done, though, regression testing can be extremely time-consuming and error-prone. ### Comparison of Automated vs Manual Regression Testing I often say that everything that’s automatable should be automated. Meaning, if you can automate a process, then you probably should do so. If you can automate a process but you’re still doing it manually, you’re leaving money on the table. Chances are the manual process is slow, time-consuming, tedious, and error-prone. ### Manual Testing Creates Opportunity Cost For starters, you waste money by having well-paid professionals performing tasks that could be automated. Then, there’s always the opportunity cost. The people who are performing the tests could be doing more valuable tasks. ### Manual Testing Is Often Error-Prone Finally, since the manual process is error-prone, then people are bound to make mistakes, which will result in losses. Automation solves that since a test script or automated test case is guaranteed to do the same thing 100% of the time. ## Automated Regression Testing: How to Put It Into Practice Now that we’ve defined some concepts, it’s time for some practical tips on how to actually implement regression testing. There’s good news. If you already write some kind of automated tests for your application—e.g. unit tests—then you’re already performing regression testing without even knowing about it. Regression testing is not a “new” category of [automated tests](/content/resources/prepare-test-automation/index.html). It’s not an alternative to unit tests or integration tests. On the contrary, your automated tests—unit tests, integration tests—can and should act as regression tests. After each new change to the codebase, just re-run all of the relevant tests on the suite to ensure they’re not failing. ## Automated Regression Testing Best Practices Additionally, there are some best practices you should implement when adopting regression testing, regardless of the specifics of your implementation: ### 1. Adopt a Test Management Software This is vital for all projects that are larger than a one-developer toy project. You’ll have, realistically, way more tests cases than you’d be able to track and manage individually. ### 2. Keep a Testing Schedule You should maintain a strict testing schedule throughout the entire project. This will ensure the final project is thoroughly tested. ### 3. Write a New Failing Test for Every New Bug Found If you find yourself in a scenario where your tests are passing despite having a bug, write a new failing test to document the bug. ### 4. Categorize All of Your Tests You should split your test suite into smaller categories. This will save your team members time by making each kind of test easily identifiable. ### 5. Keep your test cases up to date Your regression test suite should be a living thing. You’ll be constantly adding new tests as your application grows. ### 6. Care About Readability and Maintainability of Your Tests When it comes to code-based tests, treat them with the same care you treat your production code. ### 7. Make Sure Your Tests Are in Your Pipeline You want your tests to run as often as possible, which means including your regression suite as a step in your pipeline is a great idea. ## Challenges in Automated Regression Testing It’s not all a bed of roses when it comes to automated regression testing. There are significant challenges you must be aware of: 1. **Test maintenance.** The maintenance of your test suite, if not done effectively, can become a burden. 2. **Fragile tests.** Depending on [your choice of tools](/content/blog/selenium-tests-fragile/index.html), you might end up with a test suite that fails all of the time. 3. **Execution time.** As your application grows, the time required for all tests to execute could grow dramatically as well. 4. **Environment consistency.** It’s often hard to keep environments consistent. ## Integration of Automated Regression Testing into CI/CD Pipelines Ideally, you’d have all of your tests run every time someone pushes to main or merges a PR. A good compromise is to have your quick tests run often and your slower tests less frequently. ## Maintaining and Updating Automated Regression Tests ### Updates Are Necessary Understand that your regression suite will undergo changes as your application evolves. ### Maintenance Must Not Be a Burden Here are a few tips to avoid excessive burden: 1. **Prefer writing state-based tests rather than interaction-based ones.** 2. **Avoid tools that use a simplistic approach for locators.** 3. **When starting out with automated testing, prefer a risk-based approach.** ## Automated Regression Testing: Put It to Work for Your Team ASAP Software development is full of risks, including breaking existing functionality while adding new ones. If you want to get rid of regressions—then a suite of regression tests is the solution you seek. _This post was written by Carlos Schults._ [_Carlos_](http://carlosschults.net/) _is a .NET software developer with experience in both desktop and web development, and he’s now trying his hand at mobile._