diff --git a/bin/miaou-bash b/bin/miaou-bash
index c5fc94c..82b6e40 100755
--- a/bin/miaou-bash
+++ b/bin/miaou-bash
@@ -153,31 +153,39 @@ function on_error {
         print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
 
         load_tmp_error # cannot print_miaou_error after investigation
-        miaou_debug "<investigate_tmp_error pid=${BASHPID}>"
+        miaou_debug "<investigate_tmp_error_pass1 pid=${BASHPID}>"
 
         if [[ ${#tmp_error[@]} -gt 1 ]]; then
+
           local last_error regex
           last_error="${tmp_error[-2]}" # the second latest cause previous print_miaou_error above
+          miaou_debug "<analyze last_error={${last_error}} locale=$MIAOU_LOCALE>"
+
+          if [[ "$MIAOU_LOCALE" == 'fr' ]]; then
+            NBSP=$'\xc2\xa0'
+            last_error="${last_error//$NBSP/ }"
+            miaou_debug "<strip_nbsp locale=$MIAOU_LOCALE/>" # FIXME: raise issue 'commande introuvable NBSP' within fr.po!
+          fi
 
-          regex='^(.*): line ([0-9]+): (.*): command not found$'
+          regex="$MSG_COMMAND_NOT_FOUND_REGEX"
           if [[ $failure_code == 127 && "$last_error" =~ $regex ]]; then
             failure_type='COMMAND_NOT_FOUND'
             failure_payload="${BASH_REMATCH[3]}"
             miaou_debug "<command_not_found payload=${failure_payload}/>"
           else
-            regex='^(.*): line ([0-9]+): (.*): No such file or directory$'
+            regex="$MSG_FILE_NOT_FOUND_REGEX"
             if [[ $failure_code == 127 && "$last_error" =~ $regex ]]; then
               failure_type='FILE_NOT_FOUND'
               failure_payload="${BASH_REMATCH[3]}"
               miaou_debug "<file_not_found payload=${failure_payload}/>"
 
             elif ! is_true "$CHILD_PROCESS"; then
+              miaou_debug "<miaou_trace only=main>"
               # in main process only, not from children!
               local regex2 source lineno funcname
               last_error="${tmp_error[-1]}"
               regex2='^[[:space:]]+miaou_trace: source=(.*) lineno=(.*) funcname=(.*)$'
               if [[ "$last_error" =~ $regex2 ]]; then
-                miaou_debug "<miaou_trace>"
                 source="${BASH_REMATCH[1]}"
                 lineno="${BASH_REMATCH[2]}"
                 funcname="${BASH_REMATCH[3]}"
@@ -213,14 +221,14 @@ function on_error {
                     fi
                     break
                   fi
-                  # miaou_debug '</index>'
                 done
-                miaou_debug "</miaou_trace/>"
               fi
+              miaou_debug "</miaou_trace/>"
             fi
           fi
+          miaou_debug "</analyze>"
         fi
-        miaou_debug '</investigate_tmp_error>'
+        miaou_debug '</investigate_tmp_error_pass1>'
       fi
     fi
 
@@ -371,7 +379,7 @@ function dump_failure {
 }
 
 function save_err_trace_to_main {
-  miaou_debug "<save_stacktrace_to_stderr count=${#error_source[@]} to=${MIAOU_BASH_ERROR_CHILDREN}>"
+  miaou_debug "<save_backtrace_to_stderr count=${#error_source[@]} to=${MIAOU_BASH_ERROR_CHILDREN}>"
   local i source lineno funcname
   for i in "${tmp_error[@]}"; do >>"$MIAOU_BASH_ERROR_CHILDREN" echo "$i"; done
   for i in "${!error_source[@]}"; do
@@ -381,15 +389,15 @@ function save_err_trace_to_main {
     # miaou_debug "<trace source=${source} lineno=${lineno} funcname=${funcname}/>"
     >>"$MIAOU_BASH_ERROR_CHILDREN" echo -e "\tmiaou_trace: source=${source} lineno=${lineno} funcname=${funcname}"
   done
-  miaou_debug "</save_stacktrace_to_stderr>"
+  miaou_debug "</save_backtrace_to_stderr>"
 }
 
-function dump_stacktrace {
-  miaou_debug "<stacktrace count=${#error_source[@]}>"
+function dump_backtrace {
+  miaou_debug "<backtrace count=${#error_source[@]}>"
   local i source lineno funcname
   for i in "${!error_source[@]}"; do
     tty_ansi FG_MAGENTA
-    echo -n "     ╟──▷"
+    echo -n "     ╟──▷ "
     tty_ansi STYLE_ITALIC
     source="${error_source[$i]}"
     lineno="${error_lineno[$i]}"
@@ -404,7 +412,8 @@ function dump_stacktrace {
       [[ $i -gt 0 ]] && tty_ansi FG_GRAY
     fi
 
-    printf "%40s:%.4s" "$source" "$lineno"
+    local min_length=45 # TODO: compute from previous backtrace (children) and get the max
+    printf "%${min_length}s:%.4s" "$source" "$lineno"
     tty_ansi RESET
     printf " \t%s" "$funcname"
 
@@ -417,7 +426,7 @@ function dump_stacktrace {
 
     echo
   done
-  miaou_debug '</stacktrace>'
+  miaou_debug '</backtrace>'
 }
 
 function load_tmp_error {
@@ -517,9 +526,8 @@ function on_exit {
     elif [[ ! -v failure_type ]]; then
       if [[ ${#tmp_error[@]} -gt 0 ]]; then
         last_error="${tmp_error[-1]}"
-        miaou_debug "<investigate_tmp_error last={$last_error}>"
-
-        regex='^(.*): line ([0-9]+): (.*): unbound variable$'
+        miaou_debug "<investigate_tmp_error_pass2 last={$last_error}>"
+        regex="$MSG_UNBOUND_VARIABLE_REGEX"
         if [[ $failure_code -eq 1 ]] && [[ "$last_error" =~ $regex ]]; then
           failure_type='UNBOUND_VARIABLE'
           failure_payload="${BASH_REMATCH[3]}"
@@ -535,7 +543,7 @@ function on_exit {
           add_miaou_error "$source" "$line" "${failure_code}" "${failure_type}" "${failure_payload}"
           miaou_debug "<unbound_variable source=${source} line=${line} payload=${failure_payload}/>"
         else
-          regex='^(.*): line ([0-9]+): (.*): No such file or directory$'
+          regex="$MSG_SOURCE_NOT_FOUND_REGEX"
           if [[ $failure_code -eq 1 ]] && [[ "$last_error" =~ $regex ]]; then
             failure_type='SOURCE_NOT_FOUND'
             failure_payload="${BASH_REMATCH[3]}"
@@ -555,7 +563,7 @@ function on_exit {
             failure_payload="$BASH_COMMAND"
           fi
         fi
-        miaou_debug "</investigate_tmp_error>"
+        miaou_debug "</investigate_tmp_error_pass2>"
       fi
     fi
   fi
@@ -568,7 +576,7 @@ function on_exit {
       else
         2>&3 >&4 dump_failure
         if [[ -v error_source ]]; then
-          2>&3 >&4 dump_stacktrace
+          2>&3 >&4 dump_backtrace
         fi
       fi
     fi
@@ -688,6 +696,7 @@ if [[ -v SCRIPT ]]; then
   miaou_debug "<script found=$SCRIPT args_count=$#/>"
   [[ $# -gt 0 ]] && shift
 fi
+
 if is_true "$CHILD_PROCESS"; then
   # any nested children
   exec 4>/dev/tty 2>"$MIAOU_BASH_ERROR"
@@ -702,10 +711,11 @@ else
     exec 4>/dev/tty
   fi
   exec 3>&2 2>"$MIAOU_BASH_ERROR"
-  load_locale
   miaou_debug "<main file=$BASH_ARGV0 pid=${BASHPID}/>"
 fi
 
+load_locale
+
 # shellcheck source=/dev/null
 if [[ "$HEREDOC" == true ]]; then
   miaou_debug '<source heredoc/>'
diff --git a/locales/en.sh b/locales/en.sh
index f242758..7151d0f 100644
--- a/locales/en.sh
+++ b/locales/en.sh
@@ -1,2 +1,5 @@
 # shellcheck disable=SC2034
 MSG_UNBOUND_VARIABLE_REGEX='^(.*): line ([0-9]+): (.*): unbound variable$'
+MSG_COMMAND_NOT_FOUND_REGEX='^(.*): line ([0-9]+): (.*): command not found$'
+MSG_FILE_NOT_FOUND_REGEX='^(.*): line ([0-9]+): (.*): No such file or directory$'
+MSG_SOURCE_NOT_FOUND_REGEX='^(.*): line ([0-9]+): (.*): No such file or directory$'
diff --git a/locales/es.sh b/locales/es.sh
index b3e7e03..b789ea7 100644
--- a/locales/es.sh
+++ b/locales/es.sh
@@ -1,3 +1,5 @@
 # shellcheck disable=SC2034
-
-MSG_UNBOUND_VARIABLE_REGEX='^(.*): line ([0-9]+): (.*): unbound variable$'
+MSG_UNBOUND_VARIABLE_REGEX='^(.*): línea ([0-9]+): (.*): variable sin asignar$' #note the extra ' ' (compare with locale en)
+MSG_COMMAND_NOT_FOUND_REGEX='^(.*): línea ([0-9]+): (.*): orden no encontrada$'
+MSG_FILE_NOT_FOUND_REGEX='^(.*): línea ([0-9]+): (.*): No existe el fichero o el directorio$'
+MSG_SOURCE_NOT_FOUND_REGEX='^(.*): línea ([0-9]+): (.*): No existe el fichero o el directorio$'
diff --git a/locales/fr.sh b/locales/fr.sh
index f242758..70199b7 100644
--- a/locales/fr.sh
+++ b/locales/fr.sh
@@ -1,2 +1,10 @@
 # shellcheck disable=SC2034
-MSG_UNBOUND_VARIABLE_REGEX='^(.*): line ([0-9]+): (.*): unbound variable$'
+
+# note the extra ' ' (compare with locale en) => raise issue fr.po
+MSG_UNBOUND_VARIABLE_REGEX='^(.*): ligne ([0-9]+): (.*) : variable sans liaison$'
+
+# extra ' ' + weird NBSP (removed programmatically) => raise issue fr.po too
+MSG_COMMAND_NOT_FOUND_REGEX='^(.*): ligne ([0-9]+): (.*) : commande introuvable$'
+
+MSG_FILE_NOT_FOUND_REGEX='^(.*): ligne ([0-9]+): (.*): Aucun fichier ou dossier de ce nom$'
+MSG_SOURCE_NOT_FOUND_REGEX='^(.*): ligne ([0-9]+): (.*): Aucun fichier ou dossier de ce nom$'
diff --git a/test/miaou-bash.test.bash b/test/miaou-bash.test.bash
index 11d62cb..a8dd192 100755
--- a/test/miaou-bash.test.bash
+++ b/test/miaou-bash.test.bash
@@ -61,13 +61,18 @@ function assert_grep {
 
 function fail_type {
   ((test_count++))
-  local success regex hint_message
+  local success regex hint_message cmd
   success=false
   hint_message="${3:-}"
 
+  [[ -v TEST_LANG ]] && cmd="LANG=$TEST_LANG " || cmd=''
   cmd="$MIAOU_BASH_DIR/test/stub/scenario.bash $1"
-  # mapfile -t stderr <<<"$(miaou-bash ./test/stub/scenario.bash "$1" 2>&1 >/dev/null 3>/dev/null)"
-  $cmd >/dev/null 2>"$TMP_ERR" 3>"$TMP_MIAOU"
+
+  if [[ -v TEST_LANG ]]; then
+    LANG="$TEST_LANG" $cmd >/dev/null 2>"$TMP_ERR" 3>"$TMP_MIAOU"
+  else
+    $cmd >/dev/null 2>"$TMP_ERR" 3>"$TMP_MIAOU"
+  fi
   mapfile -t stderr <"$TMP_ERR"
 
   last_error="${stderr[-1]}"
@@ -83,7 +88,11 @@ function fail_type {
     return
   fi
   echo -n F
-  failures+=("$cmd")
+  if [[ -v TEST_LANG ]]; then
+    failures+=("LANG=$TEST_LANG $cmd")
+  else
+    failures+=("$cmd")
+  fi
   return 1
 }
 
@@ -199,17 +208,32 @@ time {
   assert pipe1
   assert pipe2
 
+  TEST_LANG=en_US.UTF-8 fail_type unbound_variable UNBOUND_VARIABLE
+  TEST_LANG=es_ES.UTF-8 fail_type unbound_variable UNBOUND_VARIABLE
+  TEST_LANG=fr_FR.UTF-8 fail_type unbound_variable UNBOUND_VARIABLE
+
+  TEST_LANG=en_US.UTF-8 fail_type unbound_associative UNBOUND_VARIABLE
+  TEST_LANG=es_ES.UTF-8 fail_type unbound_associative UNBOUND_VARIABLE
+  TEST_LANG=fr_FR.UTF-8 fail_type unbound_associative UNBOUND_VARIABLE
+
+  TEST_LANG=en_US.UTF-8 fail_type command_not_found COMMAND_NOT_FOUND
+  TEST_LANG=es_ES.UTF-8 fail_type command_not_found COMMAND_NOT_FOUND
+  TEST_LANG=fr_FR.UTF-8 fail_type command_not_found COMMAND_NOT_FOUND
+
+  TEST_LANG=en_US.UTF-8 fail_type source_not_found SOURCE_NOT_FOUND
+  TEST_LANG=es_ES.UTF-8 fail_type source_not_found SOURCE_NOT_FOUND
+  TEST_LANG=fr_FR.UTF-8 fail_type source_not_found SOURCE_NOT_FOUND
+
+  TEST_LANG=en_US.UTF-8 fail_type file_not_found FILE_NOT_FOUND
+  TEST_LANG=es_ES.UTF-8 fail_type file_not_found FILE_NOT_FOUND
+  TEST_LANG=fr_FR.UTF-8 fail_type file_not_found FILE_NOT_FOUND
+
+  fail_type command_error COMMAND_ERROR
   fail_type subshell_term SUBSHELL_ERROR
-  fail_type unbound_variable UNBOUND_VARIABLE
-  fail_type unbound_associative UNBOUND_VARIABLE
   fail_type false FALSE
   fail_type last_false COMMAND_ERROR
-  fail_type command_error COMMAND_ERROR
   fail_type subshell_term SUBSHELL_ERROR
   fail_type exit EXIT
-  fail_type command_not_found COMMAND_NOT_FOUND
-  fail_type source_not_found SOURCE_NOT_FOUND
-  fail_type file_not_found FILE_NOT_FOUND
   fail_type child_error CHILD_ERROR 'prefer source than child process'
 
   fail_stderr_count unbound_variable 1
@@ -223,13 +247,6 @@ time {
   fail_stderr_grep no_script 'ERROR: script expected!'
 
   assert_locales_equally_populated en es fr
-  # TODO: I18n tests for:
-  #         /opt/miaou-bash/test/stub/scenario.bash unbound_variable
-  #         /opt/miaou-bash/test/stub/scenario.bash unbound_associative
-  #         /opt/miaou-bash/test/stub/scenario.bash command_not_found
-  #         /opt/miaou-bash/test/stub/scenario.bash source_not_found
-  #         /opt/miaou-bash/test/stub/scenario.bash file_not_found
-
 }
 failed=${#failures[@]}
 success=$((test_count - failed))