panel-test-applets: 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/panel-test-applets - from package: gnome-panel-devel

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

On Debian possible default full paths are:

/usr/bin/panel-test-applets - from package: gnome-panel

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

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