What is Continuous Integration? A Comprehensive Definition for Beginners

Continuous Integration (CI) is an essential practice in modern software development, with 70% of organizations using or planning to adopt it, according to a 2019 Statista survey. By continuously merging code changes into a central repository, CI helps developers avoid project bottlenecks and ensures that their code is always up-to-date, functioning smoothly, and evolving rapidly. In this comprehensive glossary, you’ll learn about the crucial elements of CI, how it works, the advantages of using it, best practices to follow, and recommended resources to deepen your understanding.

“Continuous integration is the practice of merging all developers’ working copies to a shared mainline several times a day.” – Martin Fowler

What is Continuous Integration? Definition of CI (Continuous Integration)

Continuous Integration is a software development practice that involves the continuous merging of code changes into a central repository. As developers work on individual tasks, they frequently commit their code to this repository, where it is immediately integrated with the existing codebase. By doing so, CI enables developers to quickly identify and fix integration problems and ensure that their software remains functional, maintainable, and up-to-date.

ℹ️ Synonyms: CI, automated build, automated deployment, continuous build, continuous testing, continuous delivery, continuous deployment, CI/CD.

How it Works

To implement Continuous Integration, developers use various tools and techniques, such as version control systems, build automation, and automated testing. In a typical CI workflow, the process is as follows:

1. Developers work on their code locally, committing changes to a version control system like Git or SVN.
2. When code is committed to the central repository, the CI server automatically detects the changes and initiates a build—an automated series of steps to compile, test, and validate the code.
3. If the build is successful, it may be automatically deployed to a staging or production environment.
4. If the build fails, developers are notified of the problem, enabling them to fix the issue and commit the corrected code promptly.
5. Developers continue this loop of committing code, building, testing, and fixing errors, ensuring that their software is constantly improving and integrating smoothly.

Benefits of using Continuous Integration

• Early detection of problems: By continually integrating code, developers can uncover integration issues and bugs early, making it easier and less expensive to fix them.
• Reduced risk: CI’s regular build and test process minimizes the risk of introducing breaking changes or disruptively large modifications.
• Improved collaboration: The continuous nature of CI ensures that code is frequently reviewed and discussed, and the ongoing merging of changes prevents developers from working in isolation.
• Faster development: CI helps drive the development process forward, as frequent commits, builds, and tests establish a fast-paced, iterative workflow.
• Higher code quality: As CI promotes regular testing and validation, software quality remains a priority, resulting in more reliable and maintainable code.
• Reduced deployment anxiety: The continuous nature of CI simplifies the deployment process, making it more predictable and significantly reducing deployment-related stress.

Continuous Integration use cases

Continuous Integration is applicable across various industries and projects, with some notable use cases including:

• Web application development: CI helps web developers rapidly iterate, test, and update their applications, enabling them to deliver a high-quality user experience and adapt to changing requirements or environments.
• Mobile app development: CI streamlines the development and testing of mobile apps, ensuring that they remain compatible with the latest devices and operating systems.
• Cloud-native applications: CI enables the continuous deployment of applications to cloud platforms like AWS, GCP, and Azure, allowing developers to take full advantage of the flexibility and scalability offered by these environments.
• DevOps: Adopting CI is a critical aspect of the DevOps approach to software development, which emphasizes collaboration, automation, and rapid iteration.
• Open-source projects: CI facilitates collaboration and coordination among contributors to open-source projects, ensuring that their contributions are quickly integrated and tested within the codebase.

Code Examples

// Sample Continuous Integration (CI) pipeline using GitLab CI

image: node:12

cache:
  paths:
    - node_modules/

stages:
  - install
  - test

install_dependencies:
  stage: install
  script:
    - npm install
  artifacts:
    paths:
      - node_modules/

run_tests:
  stage: test
  script:
    - npm run test
  dependencies:
    - install_dependencies

Best Practices

While implementing Continuous Integration, adhering to a set of best practices can optimize your workflow and maximize overall effectiveness. Some of these practices include maintaining a single source repository, automating the build process, committing code frequently, testing code extensively, using feature branches/feature flags, and creating a dedicated CI environment. In addition, it is essential to prioritize clear communication and collaboration among team members, as the success of CI depends on active involvement and shared responsibility.

Most recommended books about Continuous Integration

To broaden your knowledge of Continuous Integration and discover strategies for effective implementation, consider exploring the following recommended books:

1. Continuous Integration: Improving Software Quality and Reducing Risk by Paul M. Duvall, Steve Matyas, and Andrew Glover
2. Continuous Delivery: Reliable Software Releases through Build, Test, and Deployment Automation by Jez Humble and David Farley
3. Effective CI/CD: How to Deliver Continuously Integrated and Continuously Delivered Software by Barry Luijbregts

Conclusion

Continuous Integration is a vital software development practice that fosters improvement, responsiveness, and collaboration. By embracing CI and adhering to its best practices, developers can enhance their workflows and create higher-quality software products that meet the ever-evolving needs of their users. As the IT landscape continues to evolve, Continuous Integration will remain a significant aspect of software development and a cornerstone of innovation.

Tags: agile, beginners, build automation, continuous integration, definition.