> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.tester.army/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.tester.army/_mcp/server.

# Regression Testing

Regression testing runs a predefined test group against every PR preview deployment and posts the results to the PR. Reviewers see pass/fail results directly in GitHub without leaving the review, and broken changes get caught before merge.

![Predefined tests PR comment](https://files.buildwithfern.com/testerarmy.docs.buildwithfern.com/bed46bf2975afe229d095011a6012f53f68538155c67b7245b1967f17d59faf5/docs/assets/docs/predefined-tests-comment.png)

Use this when you already know the flows that matter and want them verified the same way on every PR. To also catch issues nobody wrote a test for, pair it with the [Exploration agent](/run/pr-exploration-agent).

See [Pull Request Testing](/run/pull-request-testing) for prerequisites, supported providers, and troubleshooting.

## Setup

1. Open your project and go to the **PR Testing** tab.
2. Enable **Test groups for PR runs** and select the test group to run on pull requests. Enabled tests in this group will execute against every new deployment preview.
3. In **Integrations → Vercel**, connect Vercel and choose the matching Vercel project.
4. If Vercel deployment protection is enabled, add a [bypass token](/integrations/vercel#deployment-protection-bypass).

Optional: in **Integrations → GitHub**, choose a target branch if you only want PRs aimed at one base branch, such as `main`, to trigger automatic runs.

Every new preview deployment now triggers the selected test group automatically.

Disabled tests are skipped in PR runs but remain available for manual runs.

If the selected group uses a [Preparation Test](/run/prep-test), PR runs honor it too: the prep test runs first, web consumers reuse the saved session, and non-web consumers stay in the batch without browser-session reuse.