Delivery of a product increment requires reliable, working, integrated software at the end of every sprint. Continuous integration addresses this challenge by merging all changes made to the software and integrating all changed components regularly, at least once a day. Configuration management, compilation, software build, deployment, and testing are wrapped into a single, automated, repeatable process. Since developers integrate their work constantly, build constantly, and test constantly, defects in code are detected more quickly.
Following the developers’ coding, debugging, and check-in of code into a shared source code repository, a continuous integration process consists of the following automated activities:
- Static code analysis: executing static code analysis and reporting results
- Compile: compiling and linking the code, generating the executable files
- Unit test: executing the unit tests, checking code coverage and reporting test results
- Deploy: installing the build into a test environment
- Integration test: executing the integration tests and reporting results
- Report (dashboard): posting the status of all these activities to a publicly visible location or emailing status to the team
An automated build and test process takes place on a daily basis and detects integration errors early and quickly. Continuous integration allows Agile testers to run automated tests regularly, in some cases as part of the continuous integration process itself, and send quick feedback to the team on the quality of the code. These test results are visible to all team members, especially when automated reports are integrated into the process. Automated regression testing can be continuous throughout the iteration. Good automated regression tests cover as much functionality as possible, including user stories delivered in the previous iterations. Good coverage in the automated regression tests helps support building (and testing) large integrated systems. When the regression testing is automated, the Agile testers are freed to concentrate their manual testing on new features, implemented changes, and confirmation testing of defect fixes.