CI/CD pipeline for Express apps

Introduction

A CI/CD pipeline helps you automatically test and deliver your Express app updates quickly and safely.

When you want to automatically test your Express app after every code change.

When you want to deploy your Express app to a server without manual steps.

When you want to catch errors early before your app goes live.

When you want to speed up your development by automating builds and deployments.

When you want to keep your app updated on production with minimal effort.

Syntax

Express

name: Express CI/CD Pipeline
on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Use Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '18'
      - run: npm install
      - run: npm test
      - run: npm run build
      - name: Deploy
        run: |
          echo "Deploy commands here"

This example uses GitHub Actions syntax for a CI/CD pipeline.

Replace npm run build and deploy commands with your app's specific commands.

Examples

This simple pipeline installs dependencies and runs tests on every push.

Express

on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - run: npm install
      - run: npm test

This pipeline runs only on the main branch and deploys built files to a server.

Express

on:
  push:
    branches:
      - main
jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - run: npm install
      - run: npm run build
      - run: scp -r ./dist user@server:/var/www/app

Sample Program

This pipeline runs on pushes to the main branch. It installs dependencies, runs tests, builds the app, then copies files to a server and restarts the app process.

Express

name: Express CI/CD Pipeline
on:
  push:
    branches:
      - main
jobs:
  build-and-deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Setup Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '18'
      - name: Install dependencies
        run: npm install
      - name: Run tests
        run: npm test
      - name: Build app
        run: npm run build
      - name: Deploy to server
        run: |
          scp -r ./dist [e-mail]:/var/www/express-app
          ssh [e-mail] 'pm2 restart express-app'

Important Notes

Make sure your server allows SSH access and you have keys set up for deployment.

Use environment variables to keep secrets like server user and IP safe.

Test your pipeline with a small change before relying on it fully.

Summary

A CI/CD pipeline automates testing and deployment for your Express app.

It saves time and reduces errors by running steps automatically on code changes.

Use tools like GitHub Actions to create simple pipelines with steps for install, test, build, and deploy.

Practice

1. What is the main purpose of a CI/CD pipeline for an Express app?

easy

A. To automate testing and deployment when code changes

B. To write the Express app code manually

C. To create a user interface for the app

D. To store data in a database

Solution

1. Step 1: Understand CI/CD pipeline role

   A CI/CD pipeline automates repetitive tasks like testing and deployment to save time and reduce errors.

2. Step 2: Identify pipeline purpose for Express app

   For an Express app, the pipeline runs tests and deploys the app automatically when code changes.

3. Final Answer:

   To automate testing and deployment when code changes -> Option A

4. Quick Check:

   CI/CD automates testing and deployment [OK]

Hint: CI/CD means automatic test and deploy on code change [OK]

Common Mistakes:

• Thinking CI/CD writes code
• Confusing deployment with UI design
• Assuming CI/CD manages databases

2. Which of the following is the correct syntax to run tests in a GitHub Actions workflow for an Express app?

easy

A. execute: npm test

B. run npm test

C. run: npm test

D. command: npm test

Solution

1. Step 1: Review GitHub Actions syntax for commands

   In GitHub Actions, commands run under a step use the key 'run:' followed by the command string.

2. Step 2: Identify correct command format for tests

   To run tests with npm, the correct syntax is 'run: npm test'. Other options miss the colon or use wrong keys.

3. Final Answer:

   run: npm test -> Option C

4. Quick Check:

   GitHub Actions uses 'run:' before commands [OK]

Hint: GitHub Actions commands start with 'run:' [OK]

Common Mistakes:

• Omitting colon after 'run'
• Using 'execute' or 'command' instead of 'run'
• Writing commands without quotes or colon

3. Given this GitHub Actions step in a CI/CD pipeline for an Express app:

  - name: Install dependencies
    run: npm install
  - name: Run tests
    run: npm test

What happens if the tests fail?

medium

A. The pipeline stops and deployment does not happen

B. The pipeline ignores test failures and continues deployment

C. The pipeline retries the tests automatically

D. The pipeline skips installation and runs tests again

Solution

1. Step 1: Understand default GitHub Actions behavior on failure

   If a step like 'npm test' fails (returns error), the pipeline stops by default and does not proceed to next steps.

2. Step 2: Apply this to deployment step

   Since deployment usually comes after tests, if tests fail, deployment will not run to avoid deploying broken code.

3. Final Answer:

   The pipeline stops and deployment does not happen -> Option A

4. Quick Check:

   Failed test stops pipeline by default [OK]

Hint: Failed test stops pipeline unless configured otherwise [OK]

Common Mistakes:

• Assuming pipeline continues after test failure
• Thinking tests auto-retry without setup
• Confusing install step with test step

4. You wrote this GitHub Actions workflow snippet for your Express app:

jobs:
  ci:
    runs-on: ubuntu-latest
    steps:
      - name: Install dependencies
        run: npm install
      - name: Run tests
        run npm test
      - name: Deploy
        run: npm run deploy

What is the error in this snippet?

medium

A. Wrong command 'npm run deploy' for deployment

B. Missing colon after 'run' in the Run tests step

C. Install dependencies step should use 'npm ci' instead of 'npm install'

D. Steps should be inside a job, not directly under steps

Solution

1. Step 1: Check syntax of each step

   In GitHub Actions, each step's command must use 'run:' with a colon. The 'Run tests' step misses the colon after 'run'.

2. Step 2: Verify other steps

   'npm run deploy' is a valid command if defined in package.json scripts. 'npm install' is acceptable.

3. Final Answer:

   Missing colon after 'run' in the Run tests step -> Option B

4. Quick Check:

   GitHub Actions commands need 'run:' with colon [OK]

Hint: Check colons after 'run' in each step [OK]

Common Mistakes:

• Forgetting colon after 'run'
• Assuming 'npm run deploy' is invalid
• Confusing job structure with step syntax

5. You want to add a deployment step to your Express app's GitHub Actions pipeline that only runs when tests pass and on the main branch. Which is the best way to configure this?

hard

A. Put deploy step before tests to speed up pipeline

B. Add 'run: npm deploy' without conditions

C. Use 'if: failure()' to deploy only if tests fail

D. Use 'if: github.ref == "refs/heads/main" && success()' before the deploy step

Solution

1. Step 1: Understand conditional deployment needs

   Deployment should run only on main branch and only if tests succeed to avoid deploying broken code or on wrong branches.

2. Step 2: Use GitHub Actions condition syntax

   The 'if:' condition can check branch with 'github.ref == "refs/heads/main"' and check success with 'success()' function.

3. Final Answer:

   Use 'if: github.ref == "refs/heads/main" && success()' before the deploy step -> Option D

4. Quick Check:

   Conditional deploy uses 'if:' with branch and success check [OK]

Hint: Use 'if:' with branch and success() to control deploy [OK]

Common Mistakes:

• Deploying without branch or success check
• Deploying before tests run
• Using failure() to deploy on test failure