Continuous Integration/Continuous Deployment (CI/CD) is an essential practice in modern software development. Integrating automated tests into the CI/CD flow ensures that code is continuously tested at different stages of development, guaranteeing quality and stability. In this chapter, you will learn how to integrate Jest tests into your CI/CD pipeline.

What is CI/CD?

• Continuous Integration (CI): The practice of integrating code changes into a shared repository several times a day, followed by the automation of builds and tests.
• Continuous Deployment (CD): The practice of automatically deploying every change that passes CI tests to the production environment.

Popular CI/CD Tools

There are several tools for setting up CI/CD pipelines, including:

• GitHub Actions
• GitLab CI
• Travis CI
• Jenkins
• CircleCI

In this chapter, we will focus on how to set up Jest in GitHub Actions and GitLab CI.

GitHub Actions

GitHub Actions provides an easy and powerful way to automate workflows directly from your GitHub repository.

Setting up GitHub Actions

1. Create a workflow file: In your repository, create a file at .github/workflows/ci.yml.

2. Define the workflow: Here is an example GitHub Actions configuration to run Jest tests:

   yaml
   

GitLab CI

GitLab CI is an integrated and fully free solution for continuous integration of Git repositories.

Setting up GitLab CI

1. Create a .gitlab-ci.yml file: At the root of your repository, create a file named .gitlab-ci.yml.

2. Define the pipeline: Here is an example GitLab CI configuration to run Jest tests:

   yaml
   

Code Coverage Integration

Having visibility into code coverage is crucial in a CI/CD environment. Jest makes it easy to generate coverage reports.

Setting Up Code Coverage

1. Update Jest configuration: Ensure that Jest is configured to generate code coverage reports. Add or update your jest.config.js file with the following configuration:

   javascript
   

2. Add coverage support in your workflow (optional): You can upload coverage reports using specific integrations of each CI/CD tool or tools like Coveralls or Codecov.

   yaml
   

Complete Example: Integration with GitHub Actions

Here is a complete example of GitHub Actions configuration with code coverage integration:

yaml

[Placeholder for image: Flowchart showing a CI/CD pipeline with steps for repository checkout, dependency installation, test execution, and coverage report generation.]

Conclusion

Integrating Jest into your CI/CD flow is a crucial step to ensure the continuous quality of your code. Using tools like GitHub Actions or GitLab CI, you can automate testing, ensure that your code passes all tests before deployment, and monitor code coverage. In the following chapters, we will explore load and performance testing, as well as best practices in testing.