Building documentation for rust tests

Our testing methodology has test documentation as a first class object in the documentation output. Specifically, it defines the specification that is tested by each behavioural test.

Running cargo doc on a project with suitably documented tests doesn't yield much in the way of documentation derived from the test doc strings and I can't see any obvious way of making it include the test doc strings in the output.

Is there some way to build documentation that includes the test documentation strings?