In software engineering and development, CI (continuous integration) is a code maintainability practice. Every time we make a change to our code, we repeat the CI process to ensure the code works correctly.

CI provides fast feedback whenever a recent update causes the code to break so the programmer can work on correcting the issue before releasing updated code. CI is considered one of the basic foundations of the Agile software development methodology but we can use CI in any software development methodology. Using CI adds another level of security and ensures our code remains high-quality for the users.


How Does CI Work?

Jez Humble and David Farley describe CI in their book Continuous Delivery: Reliable Software Releases Through Build, Test, and Deployment Automation. Using CI is like having a checklist to go through every time you (or a team member) add something to the codebase.

The CI checklist has 6 items.

What Are the 6 Steps of CI?

  1. Check that the current version of the code is working correctly before introducing new changes.
  2. Ensure the recent changes execute successfully on your local server before submitting them to the codebase.
  3. If the recent changes execute successfully, add them to the codebase and check if it still works.
  4. Use a CI tool to check everything.
  5. If the build fails, check the problem, try fixing it and return to step two.
  6. If the build passes, go on to the following change or release the new version.

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Why Use CI?

For companies and individuals, catching errors and potential weaknesses in the code early on can save money and effort while maintaining a good user experience. Using CI allows you to detect these potential risks efficiently, thereby leading to a smoother path through the software development life cycle.


CI Common Practices

In order to use CI effectively in your project, make sure you:

  1. Test your build regularly.
  2. Commit new changes regularly rather than waiting until you have many changes. This will make it easier to track bugs.
  3. Improve your builds so they will be fast and simple.
  4. Make sure your tests imitate the production environment.
  5. Document bugs and errors often to avoid repeating them.
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What Are the Benefits of CI?

Incorporating CI in the development process can have several benefits for the development team. Using CI in the software development process can:

  • Save time and resources: When a development team uses CI, they can save time by fixing any risks once they occur and ensuring the code deployment is simple and efficient.
  • Scale the codebase: Using CI enables teams to scale their codebase size by eliminating the worry of code breakage at any point in the development process.
  • Clarify communication: When done properly, CI can lead to better team communication and collaboration. 
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CI Tools

There are many tools you can use to build CI pipelines while maintaining quality code readability and quality. The three most-used tools are:

  1. Jenkins: Jenkins is an open-source CI automation server that allows users to distribute tests and builds over multiple devices for better speed and efficiency. Jenkins also provides many features, such as automated unit tests and test reporting. 
  2. GitLab: GitLab is another open-source tool that can run unit and integration tests. Like Jenkins, GitLab can divide builds on multiple devices to decrease execution times. It also supports integration with tools such as Atlassian Jira and Jenkins.
  3. JetBrains is another integration and management server for CI that enables the team to test their code before they commit changes to the main code base. If a test fails, the tool sends a notification to stop integration.

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CI vs. CD: What’s the Difference?

Whenever you read about CI, it’s often combined with CD (continuous delivery). The software development process has three stages: integration, deployment and delivery. These three stages take software from idea to implementation, and finally to the end user. 

CI is the first step of that process and covers how different team members contribute to the same codebase. CI ensures their contribution doesn’t break the codebase and that they work together without clashing. 

The next step is continuous delivery. This step takes care of packaging the software for the end users, thereby ensuring the available version is always functioning. 

The last step of the development process is continuous deployment. This step automates deploying the software to the user after confirming both previous steps are passed successfully. Most tools used for CI can also be extended to include CD.

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