Day 11: Introduction to CI/CD

CI/CD is about streamlining software delivery: integrate often, test automatically, and ship in small, safe steps.

This builds on the overview in the Day 1 post.

CI vs CD

Continuous Integration (CI): merge code changes from multiple developers into a shared repository (e.g., Git) as frequently as possible. Automated builds and tests run on each integration to catch errors and conflicts early.
Continuous Deployment (CD): automatically deploy tested, verified code to production so new features and bug fixes reach users quickly and reliably.

Benefits of CI/CD

Faster feedback: automated builds and tests flag broken changes within minutes.
Improved collaboration: frequent integration keeps divergences small and conflicts rare.
Higher code quality: regression suites run on every change instead of before a big release.
Faster delivery: automation removes manual handoffs between build, test, and deploy.

CI/CD tool options

Jenkins

pipeline {
    agent any
    stages {
        stage('Checkout') {
            steps {
                git branch: 'main', url: 'https://github.com/username/repo.git'
            }
        }
        stage('Build') {
            steps {
                sh 'pip install poetry'
                sh 'poetry install'
            }
        }
        stage('Test') {
            steps {
                sh 'poetry run pytest'
            }
        }
        stage('Deliver') {
            steps {
                echo 'Codebase approved, deliver to production environment'
            }
        }
        stage('Deploy') {
            steps {
                echo 'Deploy changes to production'
                // Add your deployment steps here
            }
        }
    }
}

GitHub Actions

name: CI/CD
on: [push, pull_request]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: "3.11"
      - name: Build
        run: |
          pip install poetry
          poetry install
      - name: Test
        run: |
          poetry run pytest
      - name: Deliver
        run: |
          echo 'Codebase approved, deliver to production environment'
      - name: Deploy
        run: |
          echo 'Deploy changes to production'
          # Add your deployment steps here

CircleCI

TIP — Visual Config Editor

CircleCI has a Visual Config Editor for visualizing pipelines.

version: 2.1
jobs:
  build:
    docker:
      - image: cimg/python:3.11
    steps:
      - checkout
      - run:
          name: Build
          command: |
            pip install poetry
            poetry install
      - run:
          name: Test
          command: |
            poetry run pytest
      - run:
          name: Deliver
          command: |
            echo 'Codebase approved, deliver to production environment'
      - run:
          name: Deploy
          command: |
            echo 'Deploy changes to production'
            # Add your deployment steps here
workflows:
  version: 2
  build-deploy:
    jobs:
      - build

Travis CI

language: python
python:
  - "3.11"
install:
  - pip install poetry
  - poetry install
script:
  - poetry run pytest
after_success:
  - echo 'Codebase approved, deliver to production environment'
  - echo 'Deploy changes to production'
  # Add your deployment steps here