cjohansen/Sinon.JS — pull request #76 by ebi (2012-01-20 09:50:11+00:00)
Title: callsArgOn and callsArgOnWith

The idea is that you can pass a context to the callsArgOn functions so you can test such constructs:

Y.later(1000, this, function () {
this.doSomething(someArgument);
});

I am not sure if it is useful on yield as well, but would be happy to implement it there as well.