Mentioned links/comments during the call: 

Added product idea "Implement or incorporate a mocking framework to complement %UnitTest class" please upvote 👍 if you support the idea.

Article: Unit Tests and Test Coverage in the InterSystems Package Manager by Tim Leavitt

Evgeny Shvarov: "if you want unittest for irisbi you can leverage isc-dev module 

UnitTest_RuleSet Open Exchange solution, Unit Tests for HL7 Routing in IRIS Integration