This is a tracking bug for improvements to Inspector test harness, utilities, and other things.
I found the following 2 Testing Frameworks that are very basic comparing to other Frameworks. Both Frameworks do not expose globals and fluent-style API. The idea is to pick a Framework and run tests without a Browser dependency.
I haven't seen that Framework being used in the wild but interestingly it is already JSC compatible.
Popular Testing Framework but not JSC compatible.