Nice question Chris...
Had to think about this one. Here's a little spoofer custom app for you....
;
; IVR Loopback Tester
;
exten => *905*,1,DISA(no-password,mainmenu)
exten => *905*,2,Hangup;
Create a custom app (call it whatever you like) and paste the code above into it (make sure it has span of
internal).
Now, go to your phone and dial *905* - it will give you dial tone. Now you can tap in any of your inbound DiD numbers and it will handle them just as if they had arrived from outside. If you only have analogie lines (which don't set the DNID) then just create a PTT-DiD trunk with any old number you want. Point the PTT-DiD at your IVR and then dial the DiD number when *905* gives you dial tone.
There you go, an IVR tester in two lines of code.

Best
S