public/sh/tests/head-and-tail_test.sh

#!/usr/bin/env bash

# Unofficial Bash Strict Mode
set -euo pipefail
IFS='
'

FILENAME="student/head-and-tail.sh"

# True if FILE exists and is a regular file
if [ -f ${FILENAME} ]; then
    # FILE exists and it's not empty
    if [ -s ${FILENAME} ]; then
        if [[ $(cat $FILENAME | grep echo | wc -l) -ne 0 ]]; then
            echo "echo is not allowed in this exercise!";
            exit 1
        fi
        submitted=$(bash $FILENAME)
        expected=$(bash solutions/head-and-tail.sh)
        diff <(echo "$submitted") <(echo "$expected")
    else
        echo "The file exist but is empty"
        exit 1
    fi
else
    echo "File does not exist"
    exit 1
fi