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What is Continuous Integration (CI)?

Continuous Integration (CI) is a software development practice that automates the integration of frequent code changes from different sources to one large software project.

These isolated changes from multiple developers are added to a source repository from which builds and tests can be executed. Builds and tests aim to verify the new code’s quality, functionality, uniformity, and performance.

In other words, Continuous Integration (CI) is the automated process of continuously merging new code into a central repository after testing. It can also be explained as the routine addition of all developers’ working code changes to a shared repository every day.

Back in the days, before Continuous Integration (CI), the developer(s) would have to manually build and test any new code that they want to add to an existing project. This was very tedious and time-wasting. However, now that it’s automated, the developer(s) can focus on writing new code that matters.

Here are some Continuous Integration (CI) quotes from CI industry experts:

Continuous Integration doesn’t get rid of bugs, but it does make them dramatically easier to find and remove.” - Martin Fowler, ThoughtWorks
The earlier you catch defects, the cheaper they are to fix.” –David Farley, Continuous Delivery Author

How Does Continuous Integration (CI)?

So you might be thinking, how does Continuous Integration (CI) work? When everyone on a software engineering team is adding small continuous changes to the code base, you need a system in place that automatically builds and tests all these new code changes. The automated system will continuously build and check the new code for bugs, errors, uniformity, etc.

Here is a step by step walkthrough of the Continuous Integration (CI) process:

  1. The developers commit their code changes to the central repository.
  2. A CI (Continuous Integration) Server monitors any changes on the central repository. It then pulls the code changes, builds, and performs unit and integration tests.
  3. The CI Server (AKA Build Server) assigns a build label to the version it just built.
  4. The CI Server notifies the team of the success/failure of the build.
  5. If the build fails, the team corrects the error
  6. The process repeats

Why is Continuous Integration (CI) Important?

Continuous Integration (CI) is important because, without it, developers would have to repeatedly perform the same robotic tasks such as building new code and testing instead of writing new code, which is their core business.

Moreover, developers often work in isolation, therefore Continuous Integration (CI) improves coordination, communication, and uniformity among all members of the development team.

Continuous Integration (CI) enables developer(s) to catch unwanted events early; events include bugs, errors, and merge conflicts. The benefit of this is that since the mistake is recent, it’s easy to identify and correct.

An organization that doesn’t use a CI process often finds itself overwhelmed by:

  • The excessive amount of complex communication needed to synchronize everyone
  • Unnecessary administrative costs
  • Merge hell – extreme merge conflicts due to developer isolation
  • Disconnect within the organization as the integration process is not systemized
  • Estimate dates of delivery are unreliable

Benefits of Continuous Integration (CI)?

CI has many attractive points to any organization. Here are a few benefits that are at the core of Continuous Integration (CI):

  1. No Merge Hell

Continuous Integration (CI) prioritizes the uniformity and the seamless connectivity of each developer’s work with others’ work. The constant builds and tests by the CI server ensure that any merge conflicts are discovered quickly and are easy to fix, hence avoiding the complex and endless troubleshooting associated with merge hells.

  1. Easy to Identify and Fix Mistakes

If you encounter any bugs, errors, or merge conflicts when implementing Continuous Integration, it’s easy to pinpoint the source of the problem since you only have to check your most recent code changes. Additionally, the amount of possible mistakes is small because of the short time frame therefore it’s easy to quickly correct them.

  1. Improved Communication, Collaboration, Efficiency, and Transparency

Continuous Integration has a shared and accessible trunk (repository) which everyone can use as a guide and reference in whatever they are doing. By doing so, developers can work towards a common direction instead of working separately. Moreover, because builds and tests automation, an organization can redirect its staff’s efforts to more productive work. Administration and Supporting departments can also gain insight into a task’s progress due to CI.

Best Practices of Continuous Integration (CI)

  • Maintain one unified code repository
  • All developers must commit at least daily to the repository
  • Automate the building and testing of new code
  • Each commit must be built
  • Allow everyone to access the results of builds
  • Fix failed builds immediately
  • Automate deployment process

Continuous Integration vs Continuous Delivery vs Continuous Deployment

Continuous Integration revolves around the developers frequently committing code changes to a central repository. While Continuous Delivery includes all Continuous Integration processes but additionally extends the automation to release to a repository. Whereas Continuous Deployment includes all the previous automated Continuous Integration and Continuous Delivery steps but extends the automation to the deployment of recent changes to the public.

Continuous Deployment does everything that Continuous Delivery does and more. It entirely automates the building, merging, testing, deployment, etc. without any human intervention. Continuous Delivery requires human intervention before deployment.

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