Run Tests workflow (2020PB/police-brutality)

The Run Tests workflow from 2020PB/police-brutality, explained and optimized by Latchkey.

What it does

This is the Run Tests workflow from the 2020PB/police-brutality repository, a real project running GitHub Actions. It is shown here with attribution under its MIT license.

Below, Latchkey shows a faster, safer version produced by its optimization engine.

The workflow

name: Run Tests

on:
  pull_request:
    branches: [ main ]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    # Checks the branch out under $GITHUB_WORKSPACE, so run_tests can access it
    # `git push` would fail on `fatal: You are not currently on a branch` if `ref` was
    # not specified here.
    # Inspired by: https://peterevans.dev/posts/github-actions-how-to-automate-code-formatting-in-pull-requests/
    - uses: actions/checkout@v2
      with:
        ref: ${{ github.head_ref }}
        token: ${{ secrets.UBERSHMEKEL_ALT_TOKEN }}

    - name: Set up Python 3.7
      uses: actions/setup-python@v2
      with:
        # Semantic version range syntax or exact version of a Python version
        python-version: '3.7'

    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install -r tools/requirements.txt
        python -c "import nltk; nltk.download('wordnet')"

    - name: Run unit tests with pytest
      run: |
        pytest tools/.

The same workflow, on Latchkey

Estimated ~20% faster on cache hits, plus fewer wasted runs and a safer supply chain. Added and changed lines are highlighted.

name: Run Tests
 
on:
  pull_request:
    branches: [ main ]
 
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true
 
jobs:
  build:
    timeout-minutes: 30
    runs-on: latchkey-small
    steps:
    # Checks the branch out under $GITHUB_WORKSPACE, so run_tests can access it
    # `git push` would fail on `fatal: You are not currently on a branch` if `ref` was
    # not specified here.
    # Inspired by: https://peterevans.dev/posts/github-actions-how-to-automate-code-formatting-in-pull-requests/
    - uses: actions/checkout@v2
      with:
        ref: ${{ github.head_ref }}
        token: ${{ secrets.UBERSHMEKEL_ALT_TOKEN }}
 
    - name: Set up Python 3.7
      uses: actions/setup-python@v2
      with:
        cache: 'pip'
        # Semantic version range syntax or exact version of a Python version
        python-version: '3.7'
 
    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install -r tools/requirements.txt
        python -c "import nltk; nltk.download('wordnet')"
 
    - name: Run unit tests with pytest
      run: |
        pytest tools/.
 

What changed

• Run on Latchkey managed runners with one line (runs-on), which apply the fixes below automatically and self-heal transient failures. This example uses latchkey-small; pick the runner size that fits the job.
• Cancel superseded runs when a branch or PR gets a newer push.
• Cache dependency installs on the setup step so they are served from cache.
• Add a job timeout so a hung step cannot burn hours of runner time.

What Latchkey heals here

This workflow has steps that commonly fail on transient issues (network, registries, flaky browsers). On Latchkey managed runners they are detected, retried, and self-healed instead of failing your build:

• Dependency installs

This workflow runs 1 job per trigger. On Latchkey the same minutes cost up to 58% less than GitHub-hosted, with zero queue time.

Actions used in this workflow