> For the complete documentation index, see [llms.txt](https://docs.serverlessapigateway.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.serverlessapigateway.com/glossary/r/regression-testing.md). # Regression Testing Regression testing is the practice of re-running existing test suites after code changes to verify that previously working functionality has not been broken. It ensures that new features, bug fixes, or refactoring do not introduce unintended side effects in other parts of the system. Regression tests typically include unit tests, integration tests, and end-to-end tests that cover critical user flows and API contracts. Automated regression test suites are integrated into CI/CD pipelines to run on every code change, providing rapid feedback. The scope of regression testing can be broad (running the full test suite) or targeted (running tests related to changed components). In API development, regression testing is critical for ensuring backward compatibility. API contract tests verify that changes to backend services do not break existing clients by checking response schemas, status codes, and headers. API gateway configuration changes (such as modified routing rules or authentication policies) should also be regression tested to confirm that existing API consumers are not affected by the updates. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.serverlessapigateway.com/glossary/r/regression-testing.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.