REST-API documentation generation from unittests

I want to automatically document my REST-API. I know, there are many tools for that, but I want to generate the documentation from my unit tests.

The reason for this is, that I want the documentation to mirror, what is tested and what not. Nevertheless the documentation should be as rich as a documentation generated by let's say swagger.

I already found two projects with this approach, doctester and testdoc4j. Both do not satisfy my needs. The resulting documentation does not aggregate the happy path and the error paths.

What tools do you use and can you suggest any good one?

Cheers.