How to organize test hierarchy in CoffeeScript/JS

Ok folks, after researching couple of hours I decided to ask: I have CoffeScript class hierarchy: class B extends A, class C extends B . For example in case of Java, I would create separate test class for each of these classes, also hierarchical of course: class TestB extends TestA, etc. I want to know, how to implement unit test classes hierarchy in case of js/coffeeScript. I know, there is no direct classes in JS, so (maybe) the approach is different to run parent's test for child test class?

I am currently using mocha and not able to find Elegant solution for that. What I found could be useful is so called shared behaviours, but this is not what I need.