IOCxxTests: 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/IOCxxTests - from package: vtk-testing

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

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