Is there a way to create an object of a given type that overrides a subset of methods and throws runtime exceptions for the rest of the methods?
It doesn’t even need to have access to any implementation of the superclass. It just needs to have the same type at compiletime and runtime.
That pretty much is what a ScalaMock mock object does out of the box — methods you’ve set expectations on do whatever the expectations tell them to do, all others throw an ExpectationException.
What’s your use-case?