In GNS3, it doesn't support TDM so you cant test as in actual voice-ports. but you can test calls in other aspects depending what actually you may want;
Just to give you a high-level overview, if that may be of your interest;
What you can do is as create a topology to have multiple voice-gatewayds and create some inbound and outbound voip dial-peers to test calls.
thats actually what I did to simulate some testing for translation profiles and rules, SIP/H323 gateway etc.
you can check my blog post if you may like to see more;
Thanks, Chris, Veera and Muhammad.
The point of this was to pratice translate rules, profiles and dial-peers...
By the way, Im having a problem downloading IOS images for GNS3....
Can you privide a link for download?