Quite often, your tests will be fine when not flaring. Of course it depends on your base level compared to another person's. Someone who's been through 6 resections is probably going to always have something going on for the tests to pick up. We all are very different too. Some of us ALWAYS have a high sed rate, others almost never do. Some have blood in their stools all the time, some never do. It's a crazy, complexe little monster.
The real trick is, the various blood tests aren't even going to reliably show something when an average crohnie is flaring. If they show something that's great, but negative blood results are far from conclusive.
Tests for Crohn's disease suck. They're horribly unreliable. Even in earlier confirmed cases of crohn's disease colonoscopies only show crohn's disease 1 in 6 times. Pill cams are a little more effective at about 60% but they require small intestine involvement which not all Crohnies have. It all depends on how bad the inflammation is for where they're looking right at that moment.
Crohn's is one of the most difficult diseases to diagnose. Period. Most doctors can't handle that and do a horrible job. Your average crohn's patient goes through 6 misdiagnoses before getting the proper one. The only time Crohn's disease is reasonably easy to diagnose is when it's severe and features scar tissue which, unlike the inflammation and ulcers, is always there.
The diagnostic process for most of us is a total nightmare. Even going through it all once isn't enough. Most of the time if you get a new doctor they'll want to go through the entire process all over again because they all think they've figured out some ingenious reason why it's not really crohn's disease but instead something practically harmless or entirely curable.
The main issue with Crohn's Disease diagnostically is that it can literally be there tonight and come tomorrow morning it's gone, only to come back next week.
But, I shouldn't frighten you too much. Not ALL of us have diagnostic horror stories. Things may work out for you just fine. Good luck on your tests.