Write Unit Tests for Shell Scripts

This skill provides guidance for writing unit tests for shell scripts using Bats (Bash Automated Testing System), covering test patterns, fixtures, and best practices for production-grade shell testing. Its instructions cover confirming which shell dialects and environments are supported, setting up a test structure with helpers and fixtures, writing tests that check exit codes, output, and side effects, and adding setup and teardown so tests run cleanly in CI. Detailed examples live in a companion resources/implementation-playbook.md file.

Use it when writing unit tests for shell scripts, implementing test-driven development for scripts, setting up automated shell testing in CI/CD pipelines, testing edge cases and error conditions, or validating behavior across different shell environments. Skip it when the project does not use shell scripts, when you need integration tests beyond shell behavior, or when the goal is only linting or formatting rather than testing.

The skill itself is a set of instructions rather than a script: it walks through confirming shell dialects and environments, building a Bats test structure with helpers and fixtures, writing assertions on exit codes, output, and side effects, and wiring setup and teardown into CI. For concrete test patterns and examples it points to resources/implementation-playbook.md.

Built around Bats (Bash Automated Testing System) itself, intended to slot into whatever CI/CD pipeline already runs the shell scripts under test.

Developers and DevOps engineers maintaining shell scripts who want a structured, TDD-style approach to testing them, covering exit codes, output, error conditions, and cross-environment behavior, rather than testing shell scripts ad hoc.