Git
Git is the distributed version control system nearly all modern software teams use to track code changes, branch and merge work, and collaborate — the foundation that CI/CD pipelines, code review, and most test automation workflows are built on top of.
For testers and SDETs specifically, Git is where automated test code itself lives and evolves — test scripts, page objects, and test data get version-controlled the same way application code does, reviewed through pull requests, and run automatically by a CI pipeline triggered on every push or merge.
Git's branching model also directly shapes testing strategy — a team's branching convention (trunk-based, feature branches, release branches) determines when and how often automated tests actually run, and how quickly a regression gets caught relative to when it was introduced.
