comedi_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/comedi_test - from package: libcomedi0

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

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