Fix tests and audit TODO items

[zbuc]

There are quite a few failing tests and TODO items in the codebase that have accumulated after our recent changes.

They don't seem to be critical, as we have in fact deployed this code and are successfully relaying, however it provides a low level of assurance that subsequent changes to the code will not break anything.

At a minimum, this task should ensure:

• The tests are green in CI
• The todo!() items in the codebase have been dealt with