Continuous integration

Continuous Integration(CI) is a popular practice where changes to the code are committed often and by all members of a project into a main branch, possibly several times a day. Automating the process of ensuring that new code works and does not conflict with existing, is a goal in itself. Testing is a central part of the CI workflow. Git and GH Actions are tools that help us with this.

The ingredients of CI

• Version control for the entire codebase/project
• Automated testing of the code
• Automated building e.g. using cmake and pyproject.toml
• A platform/infrastructure for automation e.g. Github, GitLab or circleci

A first look at Github Actions

Github actions lets you automate the process of testing (and much more).

Some common use cases

• Testing
• Building and deployment
• Code quality e.g. linting and formatting
• Generating websites/documentation (this webpage)
• Code scanning (security vulnerabilities)

We will now take a first look at GH Actions using the example from Github's quickstart guide.

Step 1

We need to create a repository on Github. Have have prepared one here.

Step 2

Next, I will clone the repository locally and enter the project

git clone git@github.com:MatPiq/CI-demo.git
cd CI-demo

Step 3

We create the .github/workflows directory and add the github-actions-demo.yml file.

mkdir -p .github/workflows
touch .github/workflows/github-actions-demo.yml

The directory should look something like this:

├── .git
├── .github
│   └── workflows
│       └── github-actions-demo.yml
└── README.md

We can now paste the example workflow into github-actions-demo.yml. For example using vim:

vim .github/workflows/github-actions-demo.yml

github-actions-demo.yml

name: GitHub Actions Demo
run-name: ${{ github.actor }} is testing out GitHub Actions 🚀
on: [push]
jobs:
  Explore-GitHub-Actions:
    runs-on: ubuntu-latest
    steps:
      - run: echo "🎉 The job was automatically triggered by a ${{ github.event_name }} event."
      - run: echo "🐧 This job is now running on a ${{ runner.os }} server hosted by GitHub!"
      - run: echo "🔎 The name of your branch is ${{ github.ref }} and your repository is ${{ github.repository }}."
      - name: Check out repository code
        uses: actions/checkout@v3
      - run: echo "💡 The ${{ github.repository }} repository has been cloned to the runner."
      - run: echo "🖥️ The workflow is now ready to test your code on the runner."
      - name: List files in the repository
        run: |
          ls ${{ github.workspace }}
      - run: echo "🍏 This job's status is ${{ job.status }}."

YAML syntax

• name: Name of workflow shown under "Actions" tab
• run-name: Name specific for the run
• on: When the workflow should be triggered e.g. push, pull request (can be several)
• runs-on: Which virtual machine to run the tests on
• steps: Logically separated "tasks" in your workflow. A step can run commands or an action. Changes to environment variables are not preserved between steps.
• run:

There are many more options available that can be found here.

Step 4

We will now commit and push the changes to Github and inspect the workflow.

git add . 
git commit -m "Added demo workflow"
git push

Step 5

We can now go to "Actions" tab in the repository on Github to inspect our workflow.