ppstest: 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/ppstest - from package: pps-tools

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

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