Regression testing
Also written: Regression test
Checking that new code changes did not break existing features.
Regression testing is like checking your work after making a change. Imagine you fix a leaky faucet. Regression testing means you also check that the toilet still flushes and the shower still works. You want to be sure your fix didn't cause a new problem.
In software, when developers update code or add new features, they run regression tests. These tests are a set of checks that ensure the old parts of the software still work as expected. It's a way to catch bugs introduced by recent changes before they affect users.
Regression testing is a software quality assurance process that re-executes functional and non-functional tests to ensure that previously developed and tested software still performs correctly after a change. This change could be a modification, correction, or enhancement to the code. The goal is to detect unintended side effects of the changes in existing functionality.
Automated regression testing is common, using test suites to verify that critical paths and core features remain intact. Tradeoffs involve the cost of maintaining the test suite against the risk of releasing software with regressions. The scope of regression testing can range from a small subset of tests (selective regression) to a full suite.
Regression testing is relevant as AI models, like those used by Microsoft Copilot, are constantly updated. Developers need to ensure that new features or improvements do not negatively impact the existing functionality of these complex AI systems. This is especially important when integrating AI agents with external tools like APIs.
- How to test agent skills without hitting real APIsMicrosoft · Microsoft for Developers ·
- Microsoft Copilot
- Microsoft Copilot uses regression testing to ensure that changes to its AI agent skills do not break existing functionality, particularly when testing integrations with external APIs.
- Integration testing
- Verifies that different software modules work together corr
- Unit testing
- Tests individual components or functions of the software in isolat
- Smoke testing
- A preliminary check to ensure that the most crucial functions of
The concept of regression testing emerged with the development of software engineering practices to manage complexity and ensure stability as software evolved. It became a standard practice in the software development lifecycle.
Try using a feature in Microsoft Copilot that you know works, like asking it to summarize a document. Then, try a new feature or a slightly different command. Finally, try the original feature again to see if it still performs as expected. This simple check mimics the core idea of regression testing.
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Questions people ask
- Why is regression testing important for AI?
- AI models and agents are constantly updated. Regression testing ensures that new updates or features don't break existing, reliable functionalities, maintaining user trust and product stability.
- Is regression testing the same as testing new features?
- No, regression testing specifically checks that *old* features still work after changes. Testing new features verifies that the new additions function correctly on their own.
First seen on Subvolts Jul 17, 2026. Updated Oct 19, 2026. Written by an AI model from the items above and reviewed against them weekly; report an error.