.exactlyWith and .exactlyWhen

[mal]

I'm currently writing tests for message passing with the cluster module. In some cases it would be useful to check that a number of certain type of message were received.

What this feature request amounts to is some sort of .exactlyWith.

Additionally, consider something like .exactlyWhen which could only bump the count if the args match a filter.

spy.should.have.been.called.exactly(3).when(function (a, b) { return a > b });