Currently, the CRUD spec does not require that drivers implement a findOne helper, with a Q&A question|https://github.com/mongodb/specifications/blob/master/source/crud/crud.rst#q-a saying that it's allowed, but not required. However, due to the fact that it's not required, there isn't any coverage in the spec tests for it. Given how common it's used, I think we should at the very least add spec tests for it (which drivers that chose not to implement findOne can skip) if not make it a required part of the spec.