I've added some instrumentation and confirmed that the garbage collector can accomplish something. Thinking over this, I concluded that I want some native functions to interact with the garbage collector, and represent assertions in Lox code.
I don't want to work on that now, so I worked out some comparisons between the features of cell, limit-coverage, and mutmut-runner (which I think needs a rename). There are many underlying tasks that they all or most need to do, and some that would probably be helpful where not strictly necessary. (For example, I think I'd much rather run mutation tests in a temporary clone of a repository.) I was trying to plan this, and went too general, so I think what I should do is lay out exactly what these tools currently do, and work on converging their underlying operations.
I'll get on that tomorrow, when I'm hopefully less tired from helping move furniture.