#1089320: Update version strings and constants to 8.x tried to convert all version strings in core to D8, but it was clearly a massive grep/replace. The results in update.test and tests/* are pretty hilarious. I'm shocked that the Update manager tests are even still passing. ;) That's probably a bug in and of itself...
But, this issue is about someone who knows what's going on needs to clean up all the version information in the update manager tests so it's consistently dealing with D8.