Using concurrency, expressions, and a test matrix

Example overview

This article uses an example workflow to demonstrate some of the main CI features of GitHub Actions. When this workflow is triggered, it tests your code using a matrix of test combinations with npm test.

The following diagram shows a high level view of the workflow's steps and how they run within the job:

Diagram of an event triggering a workflow that uses a test matrix.

Features used in this example

The example workflow demonstrates the following capabilities of GitHub Actions.

Feature	Implementation
Manually running a workflow from the UI	`workflow_dispatch`
Triggering a workflow to run automatically	`pull_request`
Running a workflow at regular intervals	`schedule`
Setting permissions for the token	`permissions`
Controlling how many workflow runs or jobs can run at the same time	`concurrency`
Running the job on different runners, depending on the repository	`runs-on`
Preventing a job from running unless specific conditions are met	`if`
Using a matrix to create different test configurations	`matrix`
Cloning your repository to the runner	`actions/checkout`
Installing `node` on the runner	`actions/setup-node`
Caching dependencies	`actions/cache`
Running tests on the runner	`npm test`

Example workflow

The following workflow was created by the GitHub Docs Engineering team. To review the latest version of this file in the github/docs repository, see test.yml.

Note: Each line of this workflow is explained in the next section at "Understanding the example."

YAML

name: Node.js Tests

# **What it does**: Runs our tests.
# **Why we have it**: We want our tests to pass before merging code.
# **Who does it impact**: Docs engineering, open-source engineering contributors.

on:
  workflow_dispatch:
  pull_request:
  push:
    branches:
      - main

permissions:
  contents: read
  # Needed for the 'trilom/file-changes-action' action
  pull-requests: read

# This allows a subsequently queued workflow run to interrupt previous runs
concurrency:
  group: '${{ github.workflow }} @ ${{ github.event.pull_request.head.label || github.head_ref || github.ref }}'
  cancel-in-progress: true

jobs:
  test:
    # Run on self-hosted if the private repo or ubuntu-latest if the public repo
    # See pull # 17442 in the private repo for context
    runs-on: ${{ fromJSON('["ubuntu-latest", "self-hosted"]')[github.repository == 'github/docs-internal'] }}
    timeout-minutes: 60
    strategy:
      fail-fast: false
      matrix:
        # The same array lives in test-windows.yml, so make any updates there too.
        test-group:
          [
            content,
            graphql,
            meta,
            rendering,
            routing,
            unit,
            linting,
            translations,
          ]
    steps:
      # Each of these ifs needs to be repeated at each step to make sure the required check still runs
      # Even if if doesn't do anything
      - name: Check out repo
        uses: actions/checkout@v3
        with:
          # Not all test suites need the LFS files. So instead, we opt to
          # NOT clone them initially and instead, include them manually
          # only for the test groups that we know need the files.
          lfs: ${{ matrix.test-group == 'content' }}
          # Enables cloning the Early Access repo later with the relevant personal access token
          persist-credentials: 'false'

      - name: Figure out which docs-early-access branch to checkout, if internal repo
        if: ${{ github.repository == 'github/docs-internal' }}
        id: check-early-access
        uses: actions/github-script@v6
        env:
          BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
        with:
          github-token: ${{ secrets.DOCUBOT_REPO_PAT }}
          result-encoding: string
          script: |
            // If being run from a PR, this becomes 'my-cool-branch'.
            // If run on main, with the `workflow_dispatch` action for
            // example, the value becomes 'main'.
            const { BRANCH_NAME } = process.env
            try {
              const response = await github.repos.getBranch({
                owner: 'github',
                repo: 'docs-early-access',
                BRANCH_NAME,
              })
              console.log(`Using docs-early-access branch called '${BRANCH_NAME}'.`)
              return BRANCH_NAME
            } catch (err) {
              if (err.status === 404) {
                console.log(`There is no docs-early-access branch called '${BRANCH_NAME}' so checking out 'main' instead.`)
                return 'main'
              }
              throw err
            }

      - name: Check out docs-early-access too, if internal repo
        if: ${{ github.repository == 'github/docs-internal' }}
        uses: actions/checkout@v3
        with:
          repository: github/docs-early-access
          token: ${{ secrets.DOCUBOT_REPO_PAT }}
          path: docs-early-access
          ref: ${{ steps.check-early-access.outputs.result }}

      - name: Merge docs-early-access repo's folders
        if: ${{ github.repository == 'github/docs-internal' }}
        run: |
          mv docs-early-access/assets assets/images/early-access
          mv docs-early-access/content content/early-access
          mv docs-early-access/data data/early-access
          rm -r docs-early-access

      # This is necessary when LFS files where cloned but does nothing
      # if actions/checkout was run with `lfs:false`.
      - name: Checkout LFS objects
        run: git lfs checkout

      - name: Gather files changed
        uses: trilom/file-changes-action@a6ca26c14274c33b15e6499323aac178af06ad4b
        id: get_diff_files
        with:
          # So that `steps.get_diff_files.outputs.files` becomes
          # a string like `foo.js path/bar.md`
          output: ' '

      - name: Insight into changed files
        run: |

          # Must to do this because the list of files can be HUGE. Especially
          # in a repo-sync when there are lots of translation files involved.
          echo "${{ steps.get_diff_files.outputs.files }}" > get_diff_files.txt

      - name: Setup node
        uses: actions/setup-node@v3
        with:
          node-version: 16.14.x
          cache: npm

      - name: Install dependencies
        run: npm ci

      - name: Cache nextjs build
        uses: actions/cache@v3
        with:
          path: .next/cache
          key: ${{ runner.os }}-nextjs-${{ hashFiles('package*.json') }}

      - name: Run build script
        run: npm run build

      - name: Run tests
        env:
          DIFF_FILE: get_diff_files.txt
          CHANGELOG_CACHE_FILE_PATH: tests/fixtures/changelog-feed.json
        run: npm test -- tests/${{ matrix.test-group }}/

Understanding the example

The following table explains how each of these features are used when creating a GitHub Actions workflow.

Code	Explanation
YAML `name: Node.js Tests`	The name of the workflow as it will appear in the "Actions" tab of the GitHub repository.
YAML `on:`	The `on` keyword lets you define the events that trigger when the workflow is run. You can define multiple events here. For more information, see "Triggering a workflow."
YAML `workflow_dispatch:`	Add the `workflow_dispatch` event if you want to be able to manually run this workflow in the UI. For more information, see `workflow_dispatch`.
YAML `pull_request:`	Add the `pull_request` event, so that the workflow runs automatically every time a pull request is created or updated. For more information, see `pull_request`.
YAML `push: branches: - main`	Add the `push` event, so that the workflow runs automatically every time a commit is pushed to a branch matching the filter `main`. For more information, see `push`.
YAML `permissions: contents: read pull-requests: read`	Modifies the default permissions granted to `GITHUB_TOKEN`. This will vary depending on the needs of your workflow. For more information, see "Assigning permissions to jobs."
YAML `concurrency: group: '${{ github.workflow }} @ ${{ github.event.pull_request.head.label \|\| github.head_ref \|\| github.ref }}'`	Creates a concurrency group for specific events, and uses the `\|\|` operator to define fallback values. For more information, see "Using concurrency."
YAML `cancel-in-progress: true`	Cancels any currently running job or workflow in the same concurrency group.
YAML `jobs:`	Groups together all the jobs that run in the workflow file.
YAML `test:`	Defines a job with the ID `test` that is stored within the `jobs` key.
YAML `runs-on: ${{ fromJSON('["ubuntu-latest", "self-hosted"]')[github.repository == 'github/docs-internal'] }}`	Configures the job to run on a GitHub-hosted runner or a self-hosted runner, depending on the repository running the workflow. In this example, the job will run on a self-hosted runner if the repository is named `docs-internal` and is within the `github` organization. If the repository doesn't match this path, then it will run on an `ubuntu-latest` runner hosted by GitHub. For more information on these options see "Choosing the runner for a job."
YAML `timeout-minutes: 60`	Sets the maximum number of minutes to let the job run before it is automatically canceled. For more information, see `timeout-minutes`.
YAML `strategy:`	This section defines the build matrix for your jobs.
YAML `fail-fast: false`	Setting `fail-fast` to `false` prevents GitHub from cancelling all in-progress jobs if any matrix job fails.
YAML `matrix: test-group: [ content, graphql, meta, rendering, routing, unit, linting, translations, ]`	Creates a matrix named `test-group`, with an array of test groups. These values match the names of test groups that will be run by `npm test`.
YAML `steps:`	Groups together all the steps that will run as part of the `test` job. Each job in a workflow has its own `steps` section.
YAML `- name: Check out repo uses: actions/checkout@v3 with: lfs: ${{ matrix.test-group == 'content' }} persist-credentials: 'false'`	The `uses` keyword tells the job to retrieve the action named `actions/checkout`. This is an action that checks out your repository and downloads it to the runner, allowing you to run actions against your code (such as testing tools). You must use the checkout action any time your workflow will run against the repository's code or you are using an action defined in the repository. Some extra options are provided to the action using the `with` key.
YAML - name: Figure out which docs-early-access branch to checkout, if internal repo if: ${{ github.repository == 'github/docs-internal' }} id: check-early-access uses: actions/github-script@v6 env: BRANCH_NAME: ${{ github.head_ref \|\| github.ref_name }} with: github-token: ${{ secrets.DOCUBOT_REPO_PAT }} result-encoding: string script: \| // If being run from a PR, this becomes 'my-cool-branch'. // If run on main, with the `workflow_dispatch` action for // example, the value becomes 'main'. const { BRANCH_NAME } = process.env try { const response = await github.repos.getBranch({ owner: 'github', repo: 'docs-early-access', BRANCH_NAME, }) console.log(`Using docs-early-access branch called '${BRANCH_NAME}'.`) return BRANCH_NAME } catch (err) { if (err.status === 404) { console.log(`There is no docs-early-access branch called '${BRANCH_NAME}' so checking out 'main' instead.`) return 'main' } throw err }	If the current repository is the `github/docs-internal` repository, this step uses the `actions/github-script` action to run a script to check if there is a branch called `docs-early-access`.
YAML `- name: Check out docs-early-access too, if internal repo if: ${{ github.repository == 'github/docs-internal' }} uses: actions/checkout@v3 with: repository: github/docs-early-access token: ${{ secrets.DOCUBOT_REPO_PAT }} path: docs-early-access ref: ${{ steps.check-early-access.outputs.result }}`	If the current repository is the `github/docs-internal` repository, this step checks out the branch from the `github/docs-early-access` that was identified in the previous step.
YAML `- name: Merge docs-early-access repo's folders if: ${{ github.repository == 'github/docs-internal' }} run: \| mv docs-early-access/assets assets/images/early-access mv docs-early-access/content content/early-access mv docs-early-access/data data/early-access rm -r docs-early-access`	If the current repository is the `github/docs-internal` repository, this step uses the `run` keyword to execute shell commands to move the `docs-early-access` repository's folders into the main repository's folders.
YAML `- name: Checkout LFS objects run: git lfs checkout`	This step runs a command to check out LFS objects from the repository.
YAML - name: Gather files changed uses: trilom/file-changes-action@a6ca26c14274c33b15e6499323aac178af06ad4b id: get_diff_files with: # So that `steps.get_diff_files.outputs.files` becomes # a string like `foo.js path/bar.md` output: ' '	This step uses the `trilom/file-changes-action` action to gather the files changed in the pull request, so they can be analyzed in the next step. This example is pinned to a specific version of the action, using the `a6ca26c14274c33b15e6499323aac178af06ad4b` SHA.
YAML `- name: Insight into changed files run: \| echo "${{ steps.get_diff_files.outputs.files }}" > get_diff_files.txt`	This step runs a shell command that uses an output from the previous step to create a file containing the list of files changed in the pull request.
YAML `- name: Setup node uses: actions/setup-node@v3 with: node-version: 16.14.x cache: npm`	This step uses the `actions/setup-node` action to install the specified version of the `node` software package on the runner, which gives you access to the `npm` command.
YAML `- name: Install dependencies run: npm ci`	This step runs the `npm ci` shell command to install the npm software packages for the project.
YAML `- name: Cache nextjs build uses: actions/cache@v3 with: path: .next/cache key: ${{ runner.os }}-nextjs-${{ hashFiles('package*.json') }}`	This step uses the `actions/cache` action to cache the Next.js build, so that the workflow will attempt to retrieve a cache of the build, and not rebuild it from scratch every time. For more information, see "Caching dependencies to speed up workflows."
YAML `- name: Run build script run: npm run build`	This step runs the build script.
YAML `- name: Run tests env: DIFF_FILE: get_diff_files.txt CHANGELOG_CACHE_FILE_PATH: tests/fixtures/changelog-feed.json run: npm test -- tests/${{ matrix.test-group }}/`	This step runs the tests using `npm test`, and the test matrix provides a different value for `${{ matrix.test-group }}` for each job in the matrix. It uses the `DIFF_FILE` environment variable to know which files have changed, and uses the `CHANGELOG_CACHE_FILE_PATH` environment variable for the changelog cache file.

Next steps

To learn about GitHub Actions concepts, see "Understanding GitHub Actions."
For more step-by-step guide for creating a basic workflow, see "Quickstart for GitHub Actions."
If you're comfortable with the basics of GitHub Actions, you can learn about workflows and their features at "About workflows."