TestInstantiator: 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/TestInstantiator - from package: vtk-testing

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

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