I wouldn’t buy any testing if I didn’t know there was an ongoing infection. It’s like us human we have a lot of bacteria on us and if our flora changes the bacteria can cause to become sick even though they are natural for us to have.
It’s the same for bunnies they have bacterias on/in them that are natural but a change of normal balance can also make them sick. So not all the time they will be sick because they got an infectious bacteria. For example my previous bunny had chronic snuffles because of a bacteria that is common among rabbits. What helped him where to not expose him to stress and make sure he had a good diet. Which would not trigger his snuffle but if his immune system changed it would always kick in again.
In sweden we have a test for parasites for dogs, cats, birds and bunnies. Even among that test you can notice a small amount of the worm coccidos in bunnies. It can be active or none and depending on the amount it might not be treated specially when the bunny is all okay.