realpath.sh/test.sh

#!/bin/sh
bin=$PWD/realpath.sh
dir="$(mktemp -d)"
cd "$dir"

do_test() {
  name=$dir/$2
  target=$3
  case "$name" in
  */*) mkdir -p "${name%/*}";;
  esac

  if [ -n "$target" ]; then
    ln -sfn "$target" "$name"
  else
    touch "$name"
  fi

  is=$($bin "$name")

  should=$(readlink -f "$name")

  if [ "$is" == "$should" ]; then
    echo "Test $1 success"
  else
    echo "Test $1 fail: \"${bin##*/} $name\" returned \"$is\" instead of \"$should\""
    stat "$name"
  fi
  rm -rf "$name"
}

touch t

do_test 1 a /bin
do_test 2 a/b .
do_test 3 a/b ..
do_test 4 a/b ../t
do_test 5 a
do_test 6 a/ /bin
do_test 7 a/

rm -rf "$dir"