Continuous Integration

• CI is a development practice that requires developer to integrate code into a shared repository, multiple times.
• Each code push is then verified by a automated build system, allowing team to detect problem early.
  By integrating regularly, we can detect error quickly and locate them more easily.
• Continuous integration is cheap, not integrating continuously is expensive.
• If we don't follow a continuous approach, you will have a longer periods between integration.
  This makes it exponentially more difficult to find and fix problems, such integration problems can easily knock a project of schedule or cause it to fail altogether.

Making continuous integration works, we need:

• Source code repository
• A check-in process
• An automated build process
• A willingness to work incrementally.

Advantages of CI

1. Increase visibility, enabling better communication.
2. Catch issue early, spend less time debugging and more time in adding feature.
   • Build a solid foundation.
   • Stop waiting to find out if your code's going to work.
   • Reduce integration problems.
   • Reduce the risk of bugs.
3. It supplements the checks like:
   • Automated code quality tests.
   • Check test cases.
   • Syntax style review tools
   • Lints and formats Codebase

Martin Fowler CI

According to Martin Fowler, CI is composed of 10 key practices:

1. Maintain a single source repository.
2. Automate the build.
3. Make your build self testing.
4. Everyone commits to the mainline every day.
5. Every commit should build the main line on an integration machine.
6. Keep the build fast.
7. Test in a clone of the source in production environment.
8. Make it easy for anyone to get the latest executable.
9. Everyone can see what is happening.
10. Automate deployment.

Example : Travis

• Travis CI is a CI platform that automates the process of software testing and deployment of applications. It’s built as a platform that integrates with your GitHub projects so that you can start testing your code on the fly.
• With customers like Facebook, Mozilla, Twitter, Heroku, and others, it’s one of the leading continuous integration tools on the market.

Key Features

• Free for public open source projects on GitHub
• As simple as signing up, adding a project, and you can begin testing
• Bilingual support so your code runs smooth across all versions
• Automated pull request verification
• Works with Email, Slack, HipChat and others for easy notifications
• Extended API and CMD tools for custom management
• Cost: Free for open repositories, Enterprise for private