Why tests pass locally but fail in GitHub Actions

Check whether the same code was tested

A local branch-head test is not necessarily the same as a pull_request run. GitHub normally checks a synthetic merge result against the target branch. Record both the branch head and tested merge revision before comparing results. A conflict or change on the target branch can explain why the local check was not equivalent.

• Compare the command, working directory and selected test configuration.
• Compare runtime and package-manager versions and the dependency lockfile.
• Read the runner setup log rather than assuming its installed tools match a laptop.

Separate environment from privilege

Fork pull requests do not receive ordinary repository secrets and use a restricted GITHUB_TOKEN. A job expecting a private package registry or external credential can therefore fail only on that event. That is not permission to expose the secret to the contributor.

• Ask whether the dependency can be tested without the private service.
• Document a safe maintainer-approved test route where access is essential.
• Do not switch to pull_request_target and execute untrusted pull-request code as an access workaround.

Choose a repeatable comparison

Reproduce the failure in an authorised disposable environment using the recorded runtime, lockfile and command. Do not run an unfamiliar workflow just because it is labelled test: another job may deploy, send messages or use production services. If the problem is intermittent, retain several failing and passing run identities rather than pretending one lucky rerun explains it.

• Configuration fixes should preserve the original trigger and checks.
• A genuine application assertion failure needs a regression-test repair.
• A private-service outage or expired secret belongs outside a bounded CI configuration repair.

What proves the repair

The useful evidence is a successful execution of the same named job in the agreed event and runner context, plus the small reviewed diff and before-and-after error excerpts. A local pass or a green run on a different event can help investigation but cannot replace that acceptance evidence.