Micronaut Rails is a set of extension to deal with rails mode testing. For the moment think of it is a prototype of RSpec lite. Definitely pre alpha at the moment.
Micronaut (via spicycode-micronaut on GitHub)
No support for pure Rails fixtures, and no plans to add it - we use Factory Girl/Fixture Replacement instead, so send a patch if you want support for this).
No support for Rails integration tests – use Cucumber (github.com/aslakhellesoy/cucumber) instead!
In use in real-world projects on Rails 2.3+ - older versions may have issues.
RSpec for the great ideas and matchers