Every once in a while you need to test a relay and when you do it's important to check it thoroughly, if not you may think it's good and it's not, just because it 'clicks' doesn't mean it's good because that's only part of the equation. Yes you can swap it out with a known good relay and that will save you time but if you don't have a known good then this test should do the trick for you. This video is also a good way to get to know what's inside a relay and how it works so if you're curious about that this would be a good video to watch.