Unit testing for shell scripts

Question

Pretty much every product I\'ve worked on over the years has involved some level of shell scripts (or batch files, PowerShell etc. on Windows). Even though we wrote the bul

Answer 1

Roundup by @blake-mizerany sounds great, and I should make use of it in the future, but here is my "poor-man" approach for creating unit tests:

• Separate everything testable as a function.
• Move functions into an external file, say functions.sh and source it into the script. You can use source `dirname $0`/functions.sh for this purpose.

• At the end of functions.sh, embed your test cases in the below if condition:

  if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
  fi
  

• Your tests are literal calls to the functions followed by simple checks for exit codes and variable values. I like to add a simple utility function like the below to make it easy to write:

  function assertEquals()
  {
      msg=$1; shift
      expected=$1; shift
      actual=$1; shift
      if [ "$expected" != "$actual" ]; then
          echo "$msg EXPECTED=$expected ACTUAL=$actual"
          exit 2
      fi
  }
  

• Finally, run functions.sh directly to execute the tests.

Here is a sample to show the approach:

    #!/bin/bash
    function adder()
    {
        return $(($1+$2))
    }

    (
        [[ "${BASH_SOURCE[0]}" == "${0}" ]] || exit 0
        function assertEquals()
        {
            msg=$1; shift
            expected=$1; shift
            actual=$1; shift
            /bin/echo -n "$msg: "
            if [ "$expected" != "$actual" ]; then
                echo "FAILED: EXPECTED=$expected ACTUAL=$actual"
            else
                echo PASSED
            fi
        }

        adder 2 3
        assertEquals "adding two numbers" 5 $?
    )