But we're testing for two different things. Maybe they all have valid destinations, but some are not visible. Maybe one has an invalid destination, which would cause the test to fail at that point and then it doesn't matter how many are not visible - we won't find out about any of them. 

It's not really about the specific case, it's more about the principle - if you think something needs to be tested then make sure it actually *gets* tested. Having one test method that tests more than one thing, that could possibly fail before everything gets tested, just isn't good coverage. We should be sure that everything that we want to be tested gets tested, every time.