In a nutshell: A regression in production is a feature that was working but stops working after an update. The impact is immediate: a degraded user experience, financial losses, and teams under pressure. Common causes include poorly tested changes, a lack of automation, and accelerated deployment cycles. This guide analyzes the impact, causes, and solutions to prevent every production release from becoming a risk.
In a world where development cycles are getting shorter and shorter and production releases are coming one after another, software regressions in production pose a major challenge for companies.
A simple change to the code can lead to unexpected malfunctions, affecting product quality and the user experience.
In this article, we explore in detail the impact of production regressions, their main causes, and the most effective solutions for preventing them and minimizing their consequences.
What is a software regression in production?
A software regression refers to a malfunction in a software program or application that occurs after an update or a change to the code.
This problem occurs when features that previously worked correctly stop working or behave unexpectedly.
This may be due to a bug fix, a software update, or the addition of a new feature.
The Impact of Software Regressions in Production
Setbacks in production can have significant consequences, both from a technical standpoint and in terms of business and organizational aspects.
Impact on the User Experience
A regression that affects an application's user interface or functionality can cause frustration among users and lead to a loss of trust.
An unstable or unreliable service inevitably damages the company's brand image and can even lead to a decline in engagement or conversion rates.
A Major Financial Risk
Production setbacks can result in significant financial losses, regardless of the circumstances.
For example:
- A system failure on an e-commerce site during a traffic spike can result in a significant loss of revenue.
- A bug in financial software can cause costly transaction errors.
- A service outage requires emergency repairs, which increase maintenance and operating costs.
Disruption to development teams and internal processes
A production regression often causes significant stress for technical teams.
Developers must respond quickly, analyze and fix the problem, often outside of regular working hours.
The Main Causes of IT Setbacks
Changes that have not been tested or have been inadequately tested
One of the most common causes of regressions is the lack of adequate testing after a code change.
When a new feature is added, it may have unexpected effects on other parts of the system.
For example, in October 2018, a Windows 10 update (version 1809) caused the automatic deletion of some users' personal files (documents, images, videos).
Microsoft has released an update designed to optimize storage space on hard drives by deleting certain files deemed unnecessary. However, a bug related to the Known Folder Redirection (KFR) feature caused the system to unintentionally delete user files stored in system folders.
Lack of test automation
If non-regression tests are performed manually, there is an increased risk of missing certain errors. Insufficient test coverage can allow bugs to slip through into production.
Continuous Integration and Accelerated Deployment
With the rise of CI/CD (Continuous Integration/Continuous Deployment) practices, deployments to production have become more frequent.
However, without test automation and rigorous monitoring, the risk of regression increases significantly, which can impact the stability and performance of applications.
Non-representative test environments
If the test environment does not accurately reflect the production environment, some issues may not be detected before the system goes live.
For example, differences in server configurations or databases can lead to unexpected behavior.
Complex interactions between different modules
In complex applications, a minor change can have a ripple effect on other features due to interdependencies among software components.
In 2012, Knight Capital, a major U.S. trading firm, suffered a loss of $440 million in 45 minutes due to a software regression.
The company rolled out new trading software, but an old, obsolete feature was accidentally reactivated on one of the servers. This feature automatically executed trades, triggering a flood of erroneous buy and sell orders on the stock markets.
Preventing and Resolving Software Regressions in Production—How to Do It?
To prevent software regressions in production, regression testing must be an essential part of the testing cycle.
Essentially, it is necessary to test both existing and new features, and that is precisely what non-regression tests are designed to do.
These tests ensure that the new changes work as intended, while also ensuring that previously implemented features remain intact and free of bugs.
What is a regression test?
According to theISTQB definition, regression testing involves testing a program that has already been validated after a change has been made, to ensure that the change has not introduced new defects in parts of the software that were not modified.
In other words, a regression test verifies that changes to software, a website, or a mobile app—such as the addition of a new feature, a bug fix, or an update—have not affected the proper functioning of existing features.
For example, if an update is made to an e-commerce site to add a new payment method, a regression test will ensure that the existing payment methods (credit card, PayPal, bank transfer, etc.) continue to work even after the new option has been integrated.
*What is the difference between regression testing and non-regression testing? In reality, there is no difference; they are exactly the same thing. Both terms are used. The ISTQB, for example, prefers the term “regression testing.”
What are the different types of regression test?
Regression (or non-regression) testing can be performed in several ways, depending on the company's needs and available resources.
Fix regression tests: These reuse existing tests, provided that no major changes have been made to the product. They allow you to quickly verify that core functionality remains operational after a bug fix or minor update.
Comprehensive regression testing: This involves testing the entire product from the beginning to ensure that none of the changes made have introduced any bugs. It is often used after a major redesign or a significant update.
Selective regression testing: allows you to choose a subset of tests that target only the parts of the code affected by a change. These tests help optimize testing efforts without sacrificing coverage of critical elements.
Incremental regression testing: This involves creating new tests tailored to changes in the product, thereby ensuring better coverage of new behaviors.
Partial regression testing: performed when several modules are under development and need to be integrated into the main version of the code. This testing ensures compatibility between the new components and the entire system before merging.
Unit regression tests: These tests are designed to test specific portions of the code in isolation, without interacting with other components. They are particularly useful for quickly detecting errors in well-defined modules or features.
Avoiding Regressions in Production: Best Practices
Perform systematic non-regression tests
One of the most effective ways to prevent regressions is to systematically perform non-regression tests with every update.
These tests ensure that no changes to the code have introduced new bugs.
Ideally, non-regression tests should be performed in the following cases:
- When a bug fix is made to the code.
- When adding a new feature.
- When modifying an existing feature.
- When an environment update is performed (e.g., database change, dependency update).
- When optimizing source code to improve performance.
Follow a coding style guide
Adopting a coding style guide helps ensure consistency in code writing within a team.
These guides outline rules and best practices that all developers should follow to reduce errors and make maintenance easier.
Clear and consistently enforced rules help prevent poor programming practices that could lead to bugs that are difficult to identify and fix.
Conduct peer code reviews
Code reviews are an essential process for identifying potential errors before they are incorporated into the project.
They allow you to:
- Detect security issues and bugs before they are introduced into the source code.
- Improve code quality by drawing on the expertise of other developers.
- Ensure a better understanding of the code within the team.
Perform rigorous unit tests
Unit tests are an effective way to reduce the number of bugs that make it into production. They allow you to:
- Test each module individually, without any dependencies on the rest of the code.
- Verify the functionality of each feature individually.
- Quickly detect errors caused by code changes.
The best unit tests are written by developers who are closely involved with the project, because they know the code and its specific characteristics.
In addition,writing unit tests is an excellent way for new developers to learn how to understand existing code.
Opt for automated testing and monitoring
As your application evolves, the number of tests needed to ensure it works properly increases significantly.
This can quickly become time-consuming and resource-intensive, sometimes forcing teams to deprioritize testing in favor of other tasks.
Automating regression testing allows for faster and more frequent testing, early detection of regressions, and maximized test coverage without slowing down the development process.
Automate your regression tests with Mr Suricate
Simplify your non-regression testing and ensure an optimal user experience on your websites and mobile apps with Mr Suricate.
Take (back) control of your applications and detect bugs in real time by automating the reproduction of your user flows at regular intervals.
FAQ
What is a software regression in production?
This is the recurrence of a bug in a feature that was previously working, caused by a code change and discovered only after it went into production, so users were immediately affected by it.
What causes production setbacks?
Mainly untested or poorly tested changes, a lack of test automation, and accelerated integration and deployment cycles that leave little room for verification.
How can we prevent regressions in production?
By automating non-regression tests and integrating them into the CI/CD pipeline, we can verify with every release that the existing code still works. This is the most reliable way to deliver quickly without breaking anything.