Bats is a TAP-compliant (http://testanything.org/) testing framework for Bash. It provides a simple way to verify that the UNIX programs you write behave as expected.

A Bats test file is a Bash script with special syntax for defining test cases. Under the hood, each test case is just a function with a description.

Bats is most useful when testing software written in Bash, but you can use it to test any UNIX program.