Having traits in the stdlib would be nice, but there's also the type parameter pollution that results from mocking which I think is also a turn-off, as TFA says about rsfs.
I have a Rust library to implement the UAPI config spec (a spec that describes which files and directories a service should look for config files in), and initally wanted to test it with filesystem mocks. After making some effort to implement the mock types and traits, plus wrappers around the `<F = StdFs>` types to hide the `<F>` parameter because I didn't want to expose it in the public API, I realized it was much easier to not bother and just create all the directory trees I needed for the tests.
I have a Rust library to implement the UAPI config spec (a spec that describes which files and directories a service should look for config files in), and initally wanted to test it with filesystem mocks. After making some effort to implement the mock types and traits, plus wrappers around the `<F = StdFs>` types to hide the `<F>` parameter because I didn't want to expose it in the public API, I realized it was much easier to not bother and just create all the directory trees I needed for the tests.