ripperX_plugin_tester: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/ripperX_plugin_tester - from package: ripperx

You may install the required package with command apt-get install {package}

Error in other languages:
ripperX_plugin_tester: bevel nie gevind nie
ripperX_plugin_tester: comandă negăsită
ripperX_plugin_tester: comando não encontrado
ripperX_plugin_tester: commande introuvable
ripperX_plugin_tester: command not found
ripperX_plugin_tester: käsku ei ole
ripperX_plugin_tester: không tìm thấy lệnh
ripperX_plugin_tester: komanda nerasta
ripperX_plugin_tester: Kommando nicht gefunden.
ripperX_plugin_tester: kommandot finns inte
ripperX_plugin_tester: komut yok
ripperX_plugin_tester: nie znaleziono polecenia
ripperX_plugin_tester: níor aimsíodh an t-ordú
ripperX_plugin_tester: no se encontró la orden
ripperX_plugin_tester: no s'ha trobat l'ordre
ripperX_plugin_tester: opdracht niet gevonden
ripperX_plugin_tester: parancs nem található
ripperX_plugin_tester: perintah tidak ditemukan
ripperX_plugin_tester: príkaz nenájdený
ripperX_plugin_tester: příkaz nenalezen
ripperX_plugin_tester: команда не найдена
ripperX_plugin_tester: командата не е открита
ripperX_plugin_tester: 命令找不到
ripperX_plugin_tester: コマンドが見つかりません