> 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 A type of software testing that ensures that previously developed and tested software still performs the same way after it is changed or interfaced with other software. 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 by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` 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 what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. 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.