specrb: 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/specrb - from package: rubygem-test-spec
/usr/lib/ruby/gems/1.8/gems/test-spec-0.10.0/bin/specrb - from package: rubygem-test-spec

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

On Debian possible default full paths are:

/usr/bin/specrb - from package: ruby-test-spec

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

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