Run tests on a pr workflow (sqlalchemy/alembic)

The Run tests on a pr workflow from sqlalchemy/alembic, explained and optimized by Latchkey.

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Source: sqlalchemy/alembic.github/workflows/run-on-pr.yamlLicense MITView source

What it does

This is the Run tests on a pr workflow from the sqlalchemy/alembic 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

workflow (.yml)

name: Run tests on a pr

on:
  # run on pull request to main excluding changes that are only on doc or example folders
  pull_request:
    branches:
      - main
    paths-ignore:
      - "docs/**"

env:
  # global env to all steps
  TOX_WORKERS: -n2

permissions:
  contents: read

jobs:
  run-test-amd64:
    name: ${{ matrix.python-version }}-${{ matrix.sqlalchemy }}-${{ matrix.os }}
    runs-on: ${{ matrix.os }}
    strategy:
      # run this job using this matrix, excluding some combinations below.
      matrix:
        os:
          - "ubuntu-22.04"
        python-version:
          - "3.13"
        sqlalchemy:
          - sqla14
          - sqla20
          - sqlamain
      # abort all jobs as soon as one fails
      fail-fast: true

    # steps to run in each job. Some are github actions, others run shell commands
    steps:
      - name: Checkout repo
        uses: actions/checkout@v7

      - name: Set up python
        uses: actions/setup-python@v6
        with:
          python-version: ${{ matrix.python-version }}
          architecture: ${{ matrix.architecture }}

      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          pip install --upgrade nox setuptools
          pip list

      - name: Run tests
        run: nox -t py-${{ matrix.sqlalchemy }}

  run-pep484:
    name: pep484-${{ matrix.python-version }}-${{ matrix.os }}
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os:
          - "ubuntu-latest"
        python-version:
          - "3.12"
          - "3.13"

      fail-fast: false

    steps:
      - name: Checkout repo
        uses: actions/checkout@v7

      - name: Set up python
        uses: actions/setup-python@v6
        with:
          python-version: ${{ matrix.python-version }}
          architecture: ${{ matrix.architecture }}

      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          pip install --upgrade nox setuptools
          pip list

      - name: Run pep484
        run: nox -s pep484

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 a pr
 
on:
  # run on pull request to main excluding changes that are only on doc or example folders
  pull_request:
    branches:
      - main
    paths-ignore:
      - "docs/**"
 
env:
  # global env to all steps
  TOX_WORKERS: -n2
 
permissions:
  contents: read
 
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true
 
jobs:
  run-test-amd64:
    timeout-minutes: 30
    name: ${{ matrix.python-version }}-${{ matrix.sqlalchemy }}-${{ matrix.os }}
    runs-on: ${{ matrix.os }}
    strategy:
      # run this job using this matrix, excluding some combinations below.
      matrix:
        os:
          - "ubuntu-22.04"
        python-version:
          - "3.13"
        sqlalchemy:
          - sqla14
          - sqla20
          - sqlamain
      # abort all jobs as soon as one fails
      fail-fast: true
 
    # steps to run in each job. Some are github actions, others run shell commands
    steps:
      - name: Checkout repo
        uses: actions/checkout@v7
 
      - name: Set up python
        uses: actions/setup-python@v6
        with:
          cache: 'pip'
          python-version: ${{ matrix.python-version }}
          architecture: ${{ matrix.architecture }}
 
      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          pip install --upgrade nox setuptools
          pip list
 
      - name: Run tests
        run: nox -t py-${{ matrix.sqlalchemy }}
 
  run-pep484:
    timeout-minutes: 30
    name: pep484-${{ matrix.python-version }}-${{ matrix.os }}
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os:
          - "ubuntu-latest"
        python-version:
          - "3.12"
          - "3.13"
 
      fail-fast: false
 
    steps:
      - name: Checkout repo
        uses: actions/checkout@v7
 
      - name: Set up python
        uses: actions/setup-python@v6
        with:
          cache: 'pip'
          python-version: ${{ matrix.python-version }}
          architecture: ${{ matrix.architecture }}
 
      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          pip install --upgrade nox setuptools
          pip list
 
      - name: Run pep484
        run: nox -s pep484

What changed

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 2 jobs (5 with the matrix expanded) per trigger. On Latchkey the same minutes cost up to 58% less than GitHub-hosted, with zero queue time.

Actions used in this workflow

actions/checkout actions/setup-python