This ticket is ambiguous at the time of writing, but the motivation is to update the unit tests from the fuzzer to avoid large string comparisons on ABT dumps. Some ideas from the design:

1. Callback/registration mechanism with an overload on ABT type (similar to OnCommand helpers)
2. Tailored methods to look for a certain pattern/structure in the ABT
3. std::visit type method on ABT. Not strictly a test feature, could be useful elsewhere.
4. bindAboveBelow sort of thing, similar to the way rewrites are triggered
5. Explain to BSON, then implement helper methods to interact with that (e.g. existing tests)
6. Should we tailor helper methods to interrogate a path element sub-tree?
7. Add configurable options to ABT->BSON that collapses/simplifies that resulting tree
8. Iterator type interface, but in what order?