In reply to bborden:
The Coverage Cookbook refers to coverage in general which includes code coverage or assertion coverage. It only make sense to merge coverage from tests that pass. I think what it is trying to say is that if you have a single simulation run that consists of many tests, you need a way to not have the coverage from the failing portion of a test not included in the overall metrics.
I think what the Dolous guideline is try to say is sample the input stimulus downstream of the input ports. I don’t think that’s absolutely necessary, or at least there should be some combination of input and output coverage.