speedtest: 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/speedtest - from package: speedtest-cli

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

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