Continuous Integration
Continuous Integration (CI) is a software development practice where developers frequently integrate code changes into a shared repository, preferably several times a day. Each integration is automatically verified by building the project and running automated tests, helping to identify integration errors quickly.
Goal
The primary goal of CI is to improve software quality and accelerate the feedback loop by automating the process of integrating code changes and detecting errors early.
Context
Finding bugs late in the development cycle can be costly and time-consuming. By integrating code changes frequently and running automated tests, CI helps to identify and resolve issues quickly which helps to reduce the time to market.
CI Process
Commit Changes: As developers complete units of work, they commit code changes to the trunk. Ideally multiple times a day.
Automated Build: The CI system is configured to automatically trigger a new build whenever changes are pushed to the trunk. The CI server automatically retrieves the latest code from the repository and executes a series of steps defined in the CI pipeline. This typically includes compiling the code to ensure it builds correctly.
Automated Testing: Along with building the application, the CI pipeline executes a suite of automated tests against the build. These can include unit tests, integration tests, and any other automated tests that verify the functionality and quality of the code.
Immediate Feedback: If the build or any tests fail, the CI system alerts the team immediately, often via email, messaging systems, or through the version control interface. This allows developers to address and fix issues quickly, often within minutes of making the changes.
Fitness Function Checks: Many CI pipelines also include steps for code quality checks, security scanning, and performance testing. These tools provide additional feedback to developers about the state of their code beyond just "does it work."
Merge with Confidence: Once the build is successful and all tests pass, the changes are considered stable and can be merged into the trunk branch. This ensures that the trunk branch remains in a deployable state, facilitating continuous delivery and deployment practices.
Inputs
| Artifact | Description |
|---|---|
| Unvalidated Code | A feature that has been implemented but not yet validated with users. |
| CI Tool | The software tool that automates the CI process, including building, testing, and reporting. |
| Test Suite | A collection of tests that validate the functionality of the software. |
Outputs
| Artifact | Description | Benefits |
|---|---|---|
| Integration Feedback | Reports generated from the build and test processes, providing insights into the success or failure of integrations. | Enables quick identification and resolution of issues. |
Anti-patterns
- Manual Integration: Bypassing automated tests to speed up integrations, compromising code quality.
- Infrequent Integrations: Allowing long periods between integrations, leading to complex merges and integration issues.
- Ignoring Build Failures: Ignoring build failures or delaying fixes, allowing issues to accumulate.