zentest: 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/zentest - from package: ruby-zentest

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

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