Internet Secure Merchant Direct

I am just setting this up and home someone out there can help me figure this out.

I'm using the Internet Secure Merchant Direct 1.0 module.

I see that in the source code, there's the option for {TEST} and {TESTD} test modes, however it wasn't exposed in the module configuration so there was no way to set what mode you wanted to process in - so I exposed it in internetsecure.php

However I then noticed that isecure_usd.php appears to be a completely different beast with totally different coding than internetsecure.php

Is internetsecure.php only used to process Interac Online payments? I guess I'm just a little confused as to how to enable test mode when processing with isecure_usd.