WidgetsCxxTests: 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/WidgetsCxxTests - from package: vtk-testing

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

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