Bats Testing Patterns

This one's for anyone writing shell scripts that need proper testing. It covers Bats (Bash Automated Testing System) with patterns for unit testing your bash code, including how to test exit codes, output, and side effects. You get guidance on test structure, fixtures, setup and teardown hooks, and integrating tests into CI/CD. It's focused on TDD for shell utilities and catching edge cases before they hit production. The scope is narrow: if you're not testing shell scripts specifically, this isn't it. Includes an implementation playbook with detailed examples when you need to go deeper than the basics.