How to Trigger a Workflow on a Pull Request in GitHub Actions

The pull_request event runs your workflow against the merge result of a PR, which is exactly what you want for status checks.

Add on.pull_request and optionally narrow it with types: (opened, synchronize, reopened). The workflow checks out the merged code so tests reflect what will land.

Steps

• Add pull_request: under on.
• Optionally list types: to control which PR activity fires the run.
• Read the base and head refs from github.base_ref and github.head_ref.

Workflow

on:
  pull_request:
    types: [opened, synchronize, reopened]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci && npm test

Gotchas

• On PRs from forks, GITHUB_TOKEN is read-only and secrets are not passed, by design.
• The default types are opened, synchronize, and reopened; declaring types: replaces that set entirely.

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