NSPanelTest: 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 CentOS possible default full paths are:

/usr/bin/NSPanelTest - from package: gnustep-examples

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/NSPanelTest - from package: gnustep-examples

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

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