ovs-vlan-test: 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/ovs-vlan-test - from package: openvswitch-switch

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

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