At iThemes we officially support the latest and previous WordPress version for our plugins. This means we end up running our automated test suite across three versions, for instance right now we’re testing against WordPress 5.4, 5.5 and 5.6-beta.

Sometimes when WordPress makes a change, we need to write tests to ensure compatibility. But it only makes sense to run these tests when we’re testing on that new WordPress version. If you are running unit tests this can be fairly straightforward.