In a world of ever-shorter development cycles and fast-paced production releases, IT regressions in production represent a major challenge for companies.
A simple change in the code can lead to unexpected malfunctions, affecting product quality and the user experience.
In this article, we explore in detail the impact of regressions in production, their main causes, and the most effective solutions for preventing them and limiting their consequences.
What is an IT regression in production?
A computer regression is a software or application malfunction that occurs after an update or code modification.
This problem occurs when functions that previously worked correctly stop working or behave in an unexpected way.
This may be due to a bug fix, a software update, or the addition of a new feature.
The impact of computer regression in production
Production setbacks can have major consequences, both technically and in terms of sales and organization.
Impact on user experience
A regression impacting the user interface or the functioning of an application can generate frustration among users and lead to a loss of confidence.
An unstable or faulty service inevitably damages a company's brand image, and can even lead to a drop in engagement or conversion rates.
A major financial risk
Production setbacks can lead to substantial financial losses, whatever the context.
For example:
- A breakdown on an e-commerce site during a traffic peak can result in a significant loss of sales.
- A bug in financial software can cause costly transaction errors.
- Service interruptions require emergency interventions, increasing maintenance and operating costs.
Disruption of development teams and internal processes
Regression in production often leads to significant stress for technical teams.
Developers have to react quickly, analyzing and correcting the problem, often outside scheduled working hours.
The main causes of computer regressions
Untested or poorly tested changes
One of the most frequent causes of regression is the absence of adequate testing after a code modification.
When a new development is added, it can impact other parts of the system in unexpected ways.
For example, in October 2018, an update to Windows 10 (version 1809) caused the automatic deletion of some users' personal files (documents, images, videos).
Microsoft has introduced an update aimed at optimizing storage space on hard disks by deleting certain files considered unnecessary. However, a bug related to the Known Folder Redirection (KFR) feature led the system to unintentionally delete user files stored in system folders.
Lack of test automation
If non-regression tests are carried out manually, there is an increased risk of missing certain errors. Insufficient test coverage can let bugs pass into production.
Continuous integration and accelerated deployment
With the rise of CI/CD (Continuous Integration / Continuous Deployment) practices, production releases are more frequent.
However, without automated testing and rigorous monitoring, the risk of regression increases considerably, and can impact application stability and performance.
Non-representative test environments
If the test environment does not faithfully reflect the production environment, certain problems may not be detected before going live.
For example, differences in server or database configurations can generate unexpected behavior.
Complex interactions between different modules
In complex applications, a minor change can have cascading effects on other functionalities, due to interdependencies between software components.
In 2012, Knight Capital, a major US trading firm, suffered a $440 million loss in 45 minutes due to a software regression.
The company deployed new trading software, but an old, obsolete feature was mistakenly reactivated in one of the servers. This feature automatically executed trades, causing an avalanche of erroneous buys and sells on the stock markets.
How to prevent and resolve computer regressions in production?
To prevent IT regressions in production, regression testing must be an essential part of the test cycle.
Essentially, it is necessary to test both existing and new functionalities, and this is precisely what non-regression testing enables.
These tests ensure that new modifications work as intended, while guaranteeing that previously implemented features remain intact and bug-free.
What is a regression test?
According to theISTQB definition, a regression test consists of testing an already validated program, after a modification, to ensure that the modification has not introduced new defects in parts of the software that have not been modified.
In other words, a regression test verifies that changes to a software program, website or mobile application - such as the addition of a new feature, a bug fix or an update - have not altered the proper functioning of existing functionalities.
For example, if an update is carried out on an e-commerce site to add a new payment method, a regression test will ensure that previous payments (credit card, PayPal, bank transfer, etc.) work, even after the new option has been integrated.
*What's the difference between regression and non-regression testing? Actually, there isn't any. They're exactly the same thing. We use both terms. The ISTQB, for example, prefers the term regression test.
What are the different types of regression test?
Regression (or non-regression) testing can be carried out in a number of ways, depending on the company's needs and available resources.
Corrective regression tests: reuse existing tests, provided no major changes have been made to the product. They enable you to quickly check that basic functionality remains operational after a bug fix or minor update.
Full regression testing: involves testing the entire product from the ground up, to ensure that all modifications have introduced no anomalies. They are often used after a major redesign or update.
Selective regression testing: allows you to choose a subset of tests targeting only those parts of the code impacted by a modification. These tests optimize testing efforts without sacrificing coverage of critical elements.
Progressive regression tests: create new tests as the product evolves, ensuring better coverage of new behaviors.
Partial regression tests: carried out when several modules are being developed and need to be integrated into the main version of the code. They ensure compatibility between the new elements and the whole system before merging.
Unit regression testing: aims 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 functionalities.
Avoiding regressions in production: best practices
Perform systematic non-regression tests
One of the most effective ways of avoiding regression is to carry out non-regression tests systematically with every update.
These tests ensure that no code modifications have introduced new malfunctions.
Ideally, non-regression tests should be performed in the following cases:
- When an anomaly is corrected in 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 programming style guide
Adopting a programming style guide ensures consistency in code writing within a team.
These guides define rules and best practices to be followed by all developers in order to reduce errors and facilitate maintenance.
Clear, well-applied rules help avoid bad programming practices that can lead to regressions that are difficult to identify and correct.
Conduct peer-to-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 problems and bugs before they are introduced into source code.
- Improve code quality by benefiting from the expertise of other developers.
- Ensure a better understanding of the code within the team.
Perform rigorous unit tests
Unit testing is an effective way of reducing the number of bugs that reach production. They enable you to :
- Test each module individually, without dependency on the rest of the code.
- Check the integrity of functions in isolation.
- Quickly detect errors introduced by code modifications.
The best unit tests are written by developers close to the project, because they know the code and its specifics.
What's more,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 required to keep it running smoothly increases considerably.
This can quickly become costly in terms of time and resources, sometimes forcing us to de-prioritize testing in favor of other tasks.
Automating regression testing means you can test faster and more frequently, detect regressions early, and maximize test coverage without slowing down the development process.
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