is there a way to actually definitely test for autism comparatively late in life?

I've had a sibling that definitively has actual autism and it is impossible to say it has not had an effect on me. Just as a small example, I am exceedingly skilled at identifying autism in others, even when the non-autists around me might have no idea. I don't have the "single-field proficiency" thing that the more "high-function" autists have, but rather I have a huge issue with commitment and can't lock myself into a subject easily (same goes with transitioning between things). Speaking cohesive sentences that actually make sense is a little difficult for me and I prefer typing and writing to speaking. I never feel like I "fit in" no matter how long I spend in a group, and have trust issues.
And yet I've never been determined to actually be autistic.

Is there any sort of test for this, like a genetic identifier or something like that? If it ends up reading positive I'm jumping