What is continuous integration?
Definition: Continuous integration (CI) is a software development practice of regular code merging throughout the development team.
It allows teams to work on different parts of the code with it, automatically merging it into a single code base at set intervals in the day.
Teams use CI to detect bugs early, have a constant flow of feedback, and ensure the software they are developing remains in a working state at all times.
How does continuous integration work?
Continuous integration includes the whole team working on the same software simultaneously on different parts of its code.
This is possible through version control systems like GIT, letting them share repositories.
Every developer follows this process:
- A developer writes code on the copy of the software code base.
- The code changes are committed to a code repository.
- The commit triggers the CI system automatically, pulling the code changes from the repository.
- The CI compiles the code and runs automated tests to test if the code breaks the software.
- If it doesn’t, the CI system pushes the code changes to a testing environment. If it does, the developer is notified of the issue and returns to fixing the code and committing it again.
- The CI tests the code changes on the testing environment and validates them.
- If the code passes the test, the changes are deployed to the production environment, where they are refined. If it doesn’t, the developer is notified of the changes needed for the code to pass the test.
This process ensures that the software improvements are quick and minimizes the risk of bugs that can arise from manual deployment processes.
By automating the building and testing processes human error is eliminated and the developers can focus on writing code improving the development speed.
Continuous integration vs. continuous deployment vs. continuous delivery
Continuous Integration (CI) allows developers to merge their code changes into one codebase that is automatically compiled and tested for errors. It helps the software to run smoothly and developers to continuously improve it.
Continuous Delivery (CD) is the continuation of CI and is the process of deploying code changes automatically to the testing and building environment. It automates the release process by keeping the software ready for deployment as soon as the new build is approved, but it still needs someone to push the official release.
Continuous Deployment (CDel) automatically releases every recent change that passes all production stages without human intervention. It combines CI and CD, automating the whole process and letting the team focus on development and customer feedback.
All three methods start at the same point, but the difference is where they stop, at the integration point, release, or encompass the whole process.
Continuous integration use cases
Continuos integration has four main use cases:
- Automated Testing - CI runs automated tests on every code change ensuring the software can run with the changes and catching bugs early in the development process.
- Collaboration - CI allows multiple developers to work on the same software without facing any challenges as they work on their copies of the code that will be merged into the main code base.
- Fast Feedback - Through continuous testing, CI detects any issue with the new code submissions and informs the development team about them, preventing them from continuing to work with incorrect code.
- Path Towards Continuous Delivery - CI is the first step towards continuous delivery as it automates merging and testing new code and passes it to the production process.
In practice, CI can be applied to any software development project that requires frequent code changes, like:
Web development, as it’s usually done with multiple developers, making CI an essential practice for the whole team to work on the same code.
Mobile development to run automated tests on multiple devices and operating systems saving time from manual work.
API testing can be automated, providing developers with fast feedback if the API remains functional at all times and with all of the software it uses.
Database changes can be tested automatically using CI, ensuring that the database remains in a working state.
What is an example of continuous integration?
A development team of three is working on a new feature.
They are using GIT repositories to work on the feature simultaneously.
Every time one finishes a part of the feature code, they submit it to the code repository, and the CI system automatically pulls all the code from the code base two times a day.
It tests if the codes compile and are compatible with one another.
If everything is correct, the CI pushes the code to the main GIT branch allowing them to work on the new version.
They continue with this loop until the feature is finished without having to stop writing code.