diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..270aad7
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,6 @@
+root = true
+
+[*.sh]
+charset = utf-8
+indent_style = space
+indent_size = 2
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f2b75d1
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+**/release
diff --git a/README.md b/README.md
index 5d8adc0..af886e0 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,26 @@
 # readlink
 
-Replicate `readlink -f` as bash script using mainly dependencies available on most bash 3 platforms.
\ No newline at end of file
+Replicate `readlink -f` as bash script using mainly dependencies available on most platforms:
+
+* `readlink` (without options)
+* `cd`
+* `pwd -P`
+* `test -e` (as `[ -e <file> ]`)
+
+# Known issues
+
+* When `readlink` is part of a pipe some links contain the current pipe described like `pipe:[123456]` where the number changes on every call.  
+  `readlink` resolves these as valid links.
+
+  e.g.
+  ```
+  $ readlink -f /dev/stdout
+  /dev/pts/0
+
+  $ readlink -f /dev/stdout | cat
+  /proc/737861/fd/pipe:[2332393]
+
+  $ ./rdlink.sh /dev/stdout
+
+  ```
+  Whereas `rdlink` is not able to evaluate such links, because the pipe is already invalid as soon as a expression like `result="$(readlink "${tocheck}")"` returns.
\ No newline at end of file
diff --git a/build.sh b/build.sh
new file mode 100755
index 0000000..149e8f6
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,84 @@
+#!/usr/bin/env bash
+
+build::rdlink() {
+  readonly build_dir="$(cd "$(dirname -- "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
+  readonly rdlinkRelease="${build_dir}/release/rdlink.sh"
+  readonly color_green='\033[1;32m'
+  readonly color_red='\033[1;31m'
+  readonly color_less='\033[0m'
+  readonly shellcheck_cmd="$(command -v shellcheck)"
+  readonly fileHeader="#!/usr/bin/env bash
+
+# rdlink [OPTIONS] <PATH>
+#  [OPTION]
+#     --  :  End of options marker
+#     -*  :  Other options are ignored
+#
+# License: GNU GPL V3 or later
+#  Author: Martin Winkler
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"
+  local testresult_graphic=
+  testresult_graphic="${color_green}✔${color_less}" # alt. symbol ✓
+  testresult_graphic_fail="${color_red}✗${color_less}" # alt. symbol ≠
+
+  if ! mkdir -p "$(dirname -- "${rdlinkRelease}")" ; then
+    printf " [ERROR] Cannot create release directory\n"
+    return 1
+  fi
+
+  printf "# Building rdlink release\n"
+
+  # Write header
+  printf "%s" "${fileHeader}" > "${rdlinkRelease}"
+
+  printf "  Extracting script part and removing debug information..."
+  # Get essential script content
+  # * extract script part
+  # * remove script marker
+  #   * remove debug function calls
+  #   * remove debug options from rdlink
+  # * replace multiple empty lines with one
+  #if cat "${build_dir}/rdlink.sh" \
+  #  | sed -n '/### Script.*/,/### Script EOF/ p' \
+  #  | sed '/### Script.*/d; /^[[:blank:]]*info/d; /-d\{1,2\}/,/;;/d' \
+  #  | sed '/^$/N; /^\n$/D' \
+  #    >> "${rdlinkRelease}" 2>/dev/null ; then
+  if sed -n '/### Script.*/,/### Script EOF/ p' < "${build_dir}/rdlink.sh" \
+      | sed '/### Script.*/d; /^[[:blank:]]*info/d; /-d\{1,2\}/,/;;/d' \
+      | sed '/^$/N; /^\n$/D' \
+        >> "${rdlinkRelease}" 2>/dev/null ; then
+    printf "%b" "${testresult_graphic}\n"
+  else
+    printf "%b" "${testresult_graphic_fail}\n"
+    return 1
+  fi
+
+  if [[ "${shellcheck_cmd}" ]] ; then
+    printf "%b\n" "  Running shellcheck...\033[1A\033[s\n"
+    if "${shellcheck_cmd}" "${rdlinkRelease}" ; then
+      printf "%b" "\033[u${testresult_graphic}\n"
+    else
+      return 1
+    fi
+  fi
+
+  chmod +x "${rdlinkRelease}"
+  return 0
+}
+
+build::rdlink
+
diff --git a/rdlink.sh b/rdlink.sh
new file mode 100755
index 0000000..a51b6ed
--- /dev/null
+++ b/rdlink.sh
@@ -0,0 +1,263 @@
+#!/usr/bin/env bash
+
+## rdlink [-d|--debug] <PATH>
+##
+## License: GNU GPL V3 or later
+##  Author: Martin Winkler
+
+# Exit on error. Append "|| true" if you expect an error.
+set -o errexit
+# Exit on error inside any functions or subshells.
+set -o errtrace
+# Do not allow use of undefined vars. Use ${VAR:-} to use an undefined VAR
+set -o nounset
+# Catch the error in case mysqldump fails (but gzip succeeds) in `mysqldump |gzip`
+set -o pipefail
+
+LOG_LEVEL="${LOG_LEVEL:-1}" # 7 = debug -> 0 = emergency
+
+function rl::log () {
+  local log_level="${1:-${LOG_LEVEL}}"
+  shift
+
+  # all remaining arguments are to be printed
+  local log_line=""
+
+  while IFS=$'\n' read -r log_line; do
+    printf "%s [%9s] %s\n" "$(date -u +"%Y-%m-%d %H:%M:%S UTC")" "${log_level}" "${log_line}" 1>&2
+  done <<< "${@:-}"
+}
+emergency() {                                  rl::log emergency "${@}"; exit 1; }
+alarm()     { [[ "${LOG_LEVEL:-0}" -ge 1 ]] && rl::log alert "${@}"; true; }
+critical()  { [[ "${LOG_LEVEL:-0}" -ge 2 ]] && rl::log critical "${@}"; true; }
+error()     { [[ "${LOG_LEVEL:-0}" -ge 3 ]] && rl::log error "${@}"; true; }
+warning()   { [[ "${LOG_LEVEL:-0}" -ge 4 ]] && rl::log warning "${@}"; true; }
+notice()    { [[ "${LOG_LEVEL:-0}" -ge 5 ]] && rl::log notice "${@}"; true; }
+info()      { [[ "${LOG_LEVEL:-0}" -ge 6 ]] && rl::log info "${@}"; true; }
+debug()     { [[ "${LOG_LEVEL:-0}" -ge 7 ]] && rl::log debug "${@}"; true; }
+msg()       {                                  echo "$@"; true; }
+
+### Script
+rl::rdlink() {
+  local subject=
+  local work=
+
+  info "Processing: $*"
+  info "  with pwd: $(pwd)"
+
+  subject="$(rl::cleanpath "${1:-}")" || true
+
+  # Follow multiple symlinks
+  while subject="$(rl::quicklink "${subject}")" ; do
+    : # A link was resolved at least once
+    info "  rl::rdlink - Link found: $subject"
+  done
+
+  # Special cases handling
+  {
+    # If subject is still a link, after rl::quicklink call(s)
+    # current user has no permission to access the link itself
+    # (e.g. /proc/**/cwd)
+    if [ -L "${subject}" ] ; then
+      info "  rl::rdlink exit - can't access link ${subject}"
+      printf "\n"
+      return 1
+    fi
+  }
+
+  # Empty output if (dirname $subject) is not a valid path
+  if ! work="$(rl::canon "${subject}")" ; then
+    info "  rl::rdlink exit - invalid path ${work}"
+    printf "\n"
+    return 1
+  else
+    subject="${work}"
+  fi
+
+  printf "%s\n" "${subject}"
+}
+
+rl::quicklink() {
+  subject=
+  work=
+
+  info "Quicklink... ${1:-}"
+
+  # Check if current candidate is a symlink
+  if ! subject=$(readlink -- "${1:-}"); then
+    printf -- "%s\n" "${1:-}"
+    return 1
+  fi
+  info "  rl::quicklink symlink ${1} -> ${subject}"
+
+  # relative symlink target; prepend its parent direcotry
+  if [[ "${subject}" != "/"* ]]; then
+    work="$(rl::canon "$(dirname -- "${1:-}")")"
+    subject="${work}/${subject}"
+    info "  rl::quicklink relative link resolved: ${subject}"
+  fi
+
+  printf "%s\n" "${subject}"
+  return 0
+}
+
+rl::canon() {
+  local subject=
+  local work=
+  local bname=
+  local run=1
+  local start=
+  local retval=0
+
+  start="${1:-}"
+  info "Canonicalize path... ${start}"
+
+  while (( run )) ; do
+    if work="$(cd "${start}" >/dev/null 2>&1 && pwd -P)" ; then
+      # Special: `pwd -P` returns with // as root for links starting at /
+      # e.g. $(readlink /proc/self/root) == "/"
+      #      $(cd /proc/self/root/mnt && pwd -P) == "//mnt"
+      subject="$(rl::normalize "${work}")"
+      info "  rl::canon valid directory: ${subject}"
+      run=0
+    elif work="$(cd "$(dirname -- "${start}")" >/dev/null 2>&1 && pwd -P)" ; then
+      bname="$(basename -- "${start}")"
+
+      # Special: / produces //
+      [[ "${work}" == "/" ]] && work=
+
+      subject="${work}${bname:+"/${bname}"}"
+      info "  rl::canon valid parent: ${subject}"
+
+      # Special: Succeed with valid element after second run; see special below
+      # e.g. /root/.
+      #      * /root is valid but not accessible
+      if (( retval )) && [ -e "${subject}" ] ;then
+        info "  rl::canon valid element"
+        retval=0
+      fi
+      run=0
+    else
+      # Special: Some paths may be resolvable after normalization
+      # e.g. somedir/..
+      #      * base "somedir" does not exist
+      #      * but irrelevant because of /..
+      #      * resolves to pwd but fails by readlink -f
+      work="$(rl::normalize "${start}")"
+      if [[ "${work}" != "${start}" ]] ; then
+        info "  rl::canon retry with: ${work}"
+        start="${work}"
+        retval=1
+        continue
+      fi
+      info "  rl::canon invalid path: ${work}"
+      subject="${work}"
+      run=0 && retval=1
+    fi
+  done
+
+  printf -- "%s\n" "${subject}"
+  return ${retval}
+}
+
+rl::cleanpath() {
+  local work=
+  local rex_tmp=
+
+  info "Cleaning path... ${1:-}"
+  work="${1:-}"
+
+  # Remove multiple /
+  while [[ "${work:-}" = *"//"* ]]; do
+    work="${work//'//'/'/'}"
+  done
+
+  info "  rl::cleanpath result: ${work}"
+  printf -- "%s\n" "${work}"
+}
+
+rl::normalize() {
+  local work=
+
+  info "Normalizing path... ${1:-}"
+  work="${1:-}"
+
+  # Remove dir/.. sequences.
+  local rex_tmp='[^/][^/]*/\.\./*'
+  while [[ "${work}" =~ $rex_tmp ]] ; do
+    work="${work/"${BASH_REMATCH[0]}"/}"
+  done
+
+  # Remove /./ and /.$ sequences.
+  rex_tmp='/\.(/|$)'
+  while [[ "$work" =~ $rex_tmp ]]; do
+    work="${work/"${BASH_REMATCH[0]}"/"${BASH_REMATCH[1]/$//}"}"
+  done
+
+  # Remove leading ./
+  work="${work#./*}"
+
+  # Remove trailing /
+  rex_tmp='(.*[^/])/$'
+  if [[ "${work}" =~ $rex_tmp ]] ; then
+    work="${BASH_REMATCH[1]}"
+  fi
+
+  info "  rl::normalize result: ${work}"
+  printf -- "%s\n" "${work}"
+}
+
+rl::main() {
+  local file=
+  local arg=
+
+  for arg in "$@"; do
+    case "$arg" in
+      --)
+        shift
+        break ;;
+      -d|--debug)
+        shift
+        LOG_LEVEL=7 ;;
+      -dd)
+        shift
+        set -o xtrace ;;
+      -*)
+        shift ;;
+    esac
+  done
+
+  info "BASH rdlink"
+
+  for file in "$@"; do
+    rl::rdlink "$file"
+  done
+}
+
+# Provide as function to be called when sourced
+rdlink() {
+  rl::main "$@"
+}
+
+### Check if script is _sourced
+### https://stackoverflow.com/a/28776166
+_sourced=0
+if [ -n "${ZSH_EVAL_CONTEXT:-}" ]; then
+  case ${ZSH_EVAL_CONTEXT:-} in *:file) _sourced=1;; esac
+elif [ -n "${KSH_VERSION:-}" ]; then
+  [ "$(cd "$(dirname -- "$0")" && pwd -P)/$(basename -- "$0")" \
+    != "$(cd "$(dirname -- "${.sh.file}")" && pwd -P)/$(basename -- "${.sh.file}")" ] && _sourced=1
+elif [ -n "${BASH_VERSION:-}" ]; then
+  (return 0 2>/dev/null) && _sourced=1
+else # All other shells: examine $0 for known shell binary filenames
+  # Detects `sh` and `dash`; add additional shell filenames as needed.
+  case ${0##*/} in sh|dash) _sourced=1;; esac
+fi
+###
+
+if (( ! _sourced )); then
+  rl::main "$@"
+fi
+
+### Script EOF
+
diff --git a/test/test_rdlink.sh b/test/test_rdlink.sh
new file mode 100755
index 0000000..e9c059a
--- /dev/null
+++ b/test/test_rdlink.sh
@@ -0,0 +1,261 @@
+#!/usr/bin/env bash
+
+# Automatic tests for rdlink
+# Two kinds of tests are supported
+# * `tocompete` : competition between readlink and rdlink
+# * `toassert`  : assert expected path and input path
+
+# test_rdlink.sh [OPTIONS] [PATH TO COMPETE]
+#  [OPTIONS]
+#    -a, --run-all         : Run all tests (failed and successful)
+#    -x, --extended-output : Show more information for each test
+#    -xd                   : set -x and also show rdlink debug run for failed tests
+#    -oa, --only-assert    : Run only assert tests
+#    -oc, --only-compete   : Run only competion tests
+#    -e, --error           : Print only failed tests
+#
+# Internal tests will be executed if no arguments are found
+
+readonly test_dir="$(cd "$(dirname -- "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
+readonly tool_rdlink="${test_dir}/../release/rdlink.sh"
+readonly tool_readlink="$(command -v readlink) -f --"
+readonly build_cmd="${test_dir}/../build.sh"
+
+readonly config_path_width=45
+
+readonly color_red='\033[1;31m'
+readonly color_yellow='\033[1;33m'
+readonly color_green='\033[1;32m'
+readonly color_less='\033[0m'
+
+flag_runall=0
+flag_extendedOutput=0
+flag_verbose=0
+flag_onlyassert=0
+flag_onlycompete=0
+flag_printerror=0
+
+toassert=()
+tocompete=()
+
+. "${test_dir}/totest.sh"
+
+rl::printPath() {
+  local testnum="${1:-0}"
+  local input="${2:-"-"}"
+  local truncate_graphic=
+  local inputwidth=${config_path_width}
+
+  if (( flag_extendedOutput )); then
+    printf -- "%-3d Inp: %-${config_path_width}s ---" ${testnum} "${input}"
+  else
+    # Truncate input string on the left if longer than $config_path_width
+    if (( ${#input} > ${config_path_width} )) ; then
+      # +1 : prepending truncate_graphic
+      input="${input:$(( ${#input} - ${config_path_width} + 1 ))}"
+      # -1 : prepending truncate_graphic
+      inputwidth=$((config_path_width - 1))
+      truncate_graphic="✀"
+    fi
+    # Print input and expected
+    printf "%b%${inputwidth}s" "${truncate_graphic}" "${input}"
+  fi
+}
+
+rl::printTestSummary() {
+  local success=${1:-0}
+  local failed=${2:-0}
+  local skipped=${3:-0}
+  local total=$(( success + failed + skipped ))
+  readonly columnwidth=7
+  readonly tableformat="%${columnwidth}s | %${columnwidth}s | %${columnwidth}s | %${columnwidth}s\n"
+
+  printf "\n# Result : ${tableformat}" "success" "failed" "skipped" "total"
+  printf   "           ${tableformat}" "${success}" "${failed}" "${skipped}" "${total}"
+}
+
+# rl::testcmp <TEST NUMBER> <TEST INPUT> <EXPECTED RESULT> <ACTUAL RESULT>
+# Compare results and print summary
+rl::testcmp() {
+  local testnum="${1:-0}"
+  local input="${2:-"-"}"
+  local expect="${3:-"-"}"
+  local actual="${4:-"-"}"
+  local testresult=0 #failed
+  local testresult_graphic="${color_red}✗${color_less}" # alt. symbol ≠
+
+  if [[ "${expect}" == "${actual}" ]] ; then
+    # Don't print success for this flag
+    (( flag_printerror )) && return 0
+    testresult=1
+    testresult_graphic="${color_green}✔${color_less}" # alt. symbol ✓
+  fi
+
+  # Show only reslult as quick overview
+  if (( flag_extendedOutput )); then
+    rl::printPath ${testnum} "${input}"
+    printf " %b\n" "${testresult_graphic}"
+    if (( ! testresult )); then
+      # Test failed
+      printf " Result: %s\n    Exp: %s\n" "${actual}" "${expect}" 
+
+      if (( flag_verbose )); then
+        [ -e "${input}" ] && printf "\n Subject:\n" && ls -al "${input}"
+
+        # Print debug output of tool_a
+        printf "\n Debug:\n"
+        ( ${tool_rdlink} -d -- "${input}" )
+      fi
+      return 1
+    fi
+    return 0
+  fi
+
+  # Change result graphic if test failed
+  (( ! testresult )) && testresult_graphic="→" # "${color_green}→${color_less}"
+  rl::printPath "" "${input}"
+  printf " %b %s\n" "${testresult_graphic}" "${expect}"
+  # Print actual result if test failed
+  if (( ! testresult )); then
+    printf "%$((config_path_width))s %b %s\n" " " "${color_red}✗${color_less}" "${actual}"
+    return 1
+  fi
+  return 0
+}
+
+rl::test() {
+  local i=0
+  local path=
+  local arraywalker=
+  local firstelement=
+  local testend=0
+  local arg=
+  local excludemsg=
+  local tests_success=0
+  local tests_failed=0
+  local tests_skipped=0
+
+  for arg in "$@"; do
+    case "$1" in
+      --) ## End of options
+        shift && break ;;
+      -a|--run-all) ## Run all even if tests fail
+        flag_runall=1
+        shift ;;
+      -x|--extended-output)
+        flag_extendedOutput=1
+        shift ;;
+      -xd|--verbose)
+        flag_extendedOutput=1
+        flag_verbose=1
+        shift ;;
+      -oa|--only-assert)
+        flag_onlyassert=1
+        shift ;;
+      -oc|--only-compete)
+        flag_onlycompete=1
+        shift ;;
+      -e|--error)
+        flag_printerror=1
+        shift ;;
+      -*|--*)
+        printf "Invalid argument\n"
+        exit 1 ;;
+    esac
+  done
+
+  [[ ! -e "${tool_rdlink}" ]] && "${build_cmd}"
+
+  # Cmd line arguments
+  (( ! flag_onlycompete )) && [[ ! "$@" ]] && toassert_init
+
+  # Compare against expected result
+  if (( ${#toassert[@]} )) ; then
+    printf "\n# Assertion tests (\"Expected path\" == rdlink)\n"
+  fi
+  for testarray in "${toassert[@]}"; do
+    i=0
+    arraywalker="$testarray"[@]
+    for path in "${!arraywalker}"; do
+      if (( ! i )); then
+        # Print title in array element 0
+        printf "         ### %b ###\n" "${color_yellow}${path}${color_less}"
+        (( ! flag_extendedOutput )) && printf "%${config_path_width}s   %s %s\n" "<INPUT>" "<EXPECTED>" "✗ [ACTUAL]"
+
+      elif [ -z "$firstelement" ]; then
+        # Save first element for string compare
+        firstelement="${path}"
+
+      elif excludemsg="$(toexclude "${firstelement}")"; then
+        # Current path is excluded
+        (( tests_skipped++ ))
+        rl::printPath "$(( i/2 ))" "${firstelement}" && printf " %b skip (%s)\n" "🛇" "${excludemsg}"
+      else
+        # Execute test case
+        if ! rl::testcmp "$(( i/2 ))" "${firstelement}" \
+            "${path}" "$($tool_rdlink -- "${firstelement}")"; then
+          (( tests_failed++ ))
+          # Run all tests if option -a is pressend
+          (( ! $flag_runall )) && testend=1 && break
+        else
+          (( tests_success++ ))
+        fi
+
+        firstelement=
+      fi
+      ((i++))
+    done
+    (( testend )) && break
+  done
+  (( testend )) && rl::printTestSummary $tests_success $tests_failed $tests_skipped && return 1
+
+  # Initialize competition tests 
+  (( ! flag_onlyassert )) && tocompete_init
+
+  # Only run `compete_args` if arguments are available
+  if [[ "$@" ]]; then
+    compete_args=( "Tests from command line" "$@" )
+    tocompete=(compete_args)
+  fi
+
+  # Compare output of rdlink and readlink -f
+  if (( ${#tocompete[@]} )) ; then
+    printf "\n# Competition tests (readlink -f == rdlink)\n"
+  fi
+  for testarray in "${tocompete[@]}"; do
+    i=0
+    arraywalker="$testarray"[@]
+    for path in "${!arraywalker}"; do
+
+      if (( ! i )); then
+        # Print title in array element 0
+        printf "         ### %b ###\n" "${color_yellow}${path}${color_less}"
+        (( ! flag_extendedOutput )) && printf "%${config_path_width}s   %s %s\n" "<INPUT>" "<EXPECTED>" "✗ [ACTUAL]"
+
+      else
+        if excludemsg="$(toexclude "${path}")" ; then
+          # Current path is excluded
+          (( tests_skipped++ ))
+          rl::printPath "${i}" "${path}" && printf " %b  skip (%s)\n" "🛇" "${excludemsg}"
+        elif ! rl::testcmp "${i}" "${path}" \
+            "$(${tool_readlink} "$path")" "$(${tool_rdlink} -- "$path")"; then
+          # Test case failed
+          (( tests_failed++ ))
+          # Run all tests if option -a is pressend
+          (( ! $flag_runall )) && testend=1 && break
+        else
+          (( tests_success++ ))
+        fi
+      fi
+
+      ((i++))
+    done
+    (( testend )) && break
+  done
+
+  rl::printTestSummary $tests_success $tests_failed $tests_skipped
+  (( testend )) && return 1 || return 0
+}
+
+#time rl::test "$@"
+rl::test "$@"
diff --git a/test/totest.sh b/test/totest.sh
new file mode 100644
index 0000000..f26be7a
--- /dev/null
+++ b/test/totest.sh
@@ -0,0 +1,207 @@
+#!/usr/bin/env bash
+
+########## Competition Block ##########
+
+# tc = test compete
+_tc_tmp="${test_dir:-"/tmp"}/tmp_compete"
+
+# Each competition link is given to both tools
+# and the output is compared
+#
+# Array format:
+# [0] = Title
+# [1] = path for competition
+# [2] = path for competition
+# ...
+
+# Compete test suites (arrays) 
+compete_canonicalize=( "Canonicalize invalid path"
+  "///tmp//./b"
+  "//tmp//./b/.."
+  "//tmp//./b/."
+  "//tmp//./b/"
+  "///notthere//...../help/."
+)
+
+compete_relative=( "Resolving of relative links"
+  # Invalid
+  "nofile_l"
+  "nopath_l"
+  # Valid
+  "dir_1/file" # Valid relative link to path with relative element
+)
+
+compete_all=( "Test - everything starting from /"
+  /**/*
+)
+
+
+tocompete_init() {
+  # initialize custom test structure
+  {
+    mkdir -p "${_tc_tmp}"
+    cd "${_tc_tmp}"
+
+    # compete_links
+    touch "${_tc_tmp}/a"
+    ln -s "${_tc_tmp}/a" "${_tc_tmp}/a 2"
+    ln -s "${_tc_tmp}/a 2" "${_tc_tmp}/a 3"
+    mkdir -p "dir_1"
+    mkdir -p "dir_2/dir_22"
+    touch "dir_2/dir_22/file"
+    ln -s "dir_2/dir_22" "dir_3_l"
+    ln -s "../dir_3_l/file" "dir_1/file"
+
+    # compete_no_permission
+    mkdir -p "${_tc_tmp}/noperm"
+    chmod 400 "${_tc_tmp}/noperm"
+    ln -s "noperm" "${_tc_tmp}/noperml"
+    ln -s "/" "${_tc_tmp}/lroot"
+    ln -s "/root" "${_tc_tmp}/lroothome"
+
+    # compete_relative
+    ln -s "../nofile" "${_tc_tmp}/nofile_l"
+    ln -s "../nodir/nofile" "${_tc_tmp}/nopath_l"
+
+    #echo "rl: " && readlink "${_tc_tmp}/lnoperm"  
+    #ls -l "${_tc_tmp}"
+  }
+
+  # Base directory for the test
+  cd "${_tc_tmp}"
+
+
+  # Compete test arrays with "dynamic" cases need to be inside the init function
+  # e.g. "$(cd ../test && pwd)/file" - base directory must be set first
+  # e.g. "${_tc_tmp}/"* - _tc_tmp must be populated first
+  compete_invalid=( "Invalid files with and without valid path"
+    "${_tc_tmp}/invalid_file"
+    "/invalid_file"
+    "/invalid_direcotry/invalidfile"
+    "-v" # Not recommended file naming
+    "../-v" # Not recommended file naming
+    "-v/.." # Not recommended file naming
+  )
+
+  compete_links=( "Test - Valid links"
+    "${_tc_tmp}/a 3" # slink chain a3 -> a2 -> a
+    "${_tc_tmp}/a"*
+    "/dev/stdin"
+    #"/dev/stdout" skip - Always different
+    #"/dev/fd" # Test skip - /dev/fd is different on every call
+    #"/etc/mtab" # skip - Always different
+    #"/proc/mounts" # skip - Always different
+    #"/proc/net/"* # skip - Always different
+  )
+
+  compete_no_permission=( "No permission to enter directory (direct and link)"
+    "noperm"*
+    "lroot"*
+    "/"
+    "/root"
+    "/root/"
+    "/root/."
+    "/root/.."
+    "/proc/"**/cwd # special - no permission for links 
+  )
+
+  # Add tests to global test array from test_rdlink
+  tocompete+=(
+    compete_canonicalize
+    compete_invalid
+    compete_relative
+    compete_no_permission
+    compete_links
+    compete_all
+  )
+}
+
+tocompete_clean() {
+  rm -rf "${_tc_tmp}" 
+}
+
+########## Assertion Block ##########
+
+# ta = test assert
+_ta_tmp="${test_dir:-"/tmp"}/tmp_assert"
+
+# Assertion string compare test arrays
+#
+# Array format
+# [0] = Title
+# [1] input == [2] expected
+# [3] input == [4] expected
+# ...
+
+toassert_init() {
+  {
+    mkdir -p "${_ta_tmp}"
+  }
+
+  # Base directory for the test
+  cd "${_ta_tmp}"
+
+  # Assert test arrays with "dynamic" cases need to be inside the init function
+  # e.g. "$(cd ../test && pwd)/file" - base directory must be set first
+  # e.g. "${_tc_tmp}/"* - _tc_tmp must be populated first
+  assert_invalid_files=( "Assert - invalid files"
+    "${_ta_tmp}/missing_file" "${_ta_tmp}/missing_file"
+    "${_ta_tmp}/missd/missf" ""
+    "${_ta_tmp}/miss c" "${_ta_tmp}/miss c"
+    "rel_a" "${_ta_tmp}/rel_a"
+    "../rel_b" "$(cd ".." && pwd)/rel_b"
+  )
+
+  # Add test arrays to global test array from test_rdlink
+  toassert+=(
+    assert_invalid_files
+  )
+}
+
+toassert_clean() {
+  rm -rf "${_ta_tmp}"
+}
+
+########## Common data and functions ##########
+#
+# [0] exclude regex [1] Reason for exclution
+# [2] exclude regex [3] Reason for exclution
+exclude_path=(
+  "/dev/fd$" "Different on every call"
+  "/dev/stdout$" "Always different in pipes"
+  "/etc/mtab$" "Different on every call"
+  "/proc/mounts$" "Different on every call"
+  "/proc/net$" "Different on every call"
+  "/proc/net/.*" "Different on every call"
+  "/proc/self/fd/(1|3|255)" "Different on every call"
+  "/proc/self$" "Different on every call"
+  "/proc/self/(attr|fdinfo|map_files|net|ns|task)/.*" "Different on every call"
+  "/proc/thread-self$" "Different on every call"
+)
+
+toexclude() {
+  local path=
+  local exclude=
+  for path in "${exclude_path[@]}" ; do
+    if [[ ! "${exclude}" ]] ; then
+      exclude="${path}"
+    else 
+      # return reason for exclution
+      if [[ "${1:-}" =~ ${exclude} ]] ; then
+        printf "${path}"
+        return 0
+      fi
+      exclude=
+    fi
+  done
+  return 1
+}
+
+########## Clean custom test data ##########
+#
+totest_cleanall() {
+  tocompete_clean
+  toassert_clean
+}
+trap totest_cleanall EXIT
+