gfal_unittest: 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/gfal_unittest - from package: gfal-doc

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

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