MSC_Tests.ttcn: introduce TC_mt_ussd_for_unknown_subscr

The idea of this test case is to check that OsmoMSC properly
rejects SS/USSD requests for unknown subscribers.

Running this test case against the current OsmoMSC helped
to discover several problems:

  - OsmoMSC doesn't print anything in such cases;
  - IMSI in the response error message is empty;
  - both session state and ID IEs are omited;

which are going to be fixed soon.

Change-Id: Id35cd3ec15d1bab15260312d7bbb41e2d10349fe
Related: OS#2931
1 file changed