varnishtest: 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/varnishtest - from package: varnish

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

On Debian possible default full paths are:

/usr/bin/varnishtest - from package: varnish

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

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