I had an edible containing THC on April 4th and 5th, and I was wondering if I will be able to pass a hair test that is coming up within 30 days. Any thoughts?

Is this the only Pot you ingested? Smoked? If it is, than you should be fine. Hair follicle tests test for habitual use not single use. You would need to smoke up a lot for it to appear.

I had only consumed one time before that which was last year in about October. Other than that, I have not smoked or anything else with THC. Is there anything I can do just to be safe?

Nope.

The evidence is in your hair already. The best way is to not doing it. That horse is out of the barn. Just need to hope that there isn't enough to damn you. You should be good though.

It depends on how much you ingested and how powerful the THC content was. But a hair drug test is meant to show consistent use over time of a particular drug and at this point I doubt if you did enough to show a positive on a hair drug test.

I ate approximately 1 gram of marijuana. I feel like I haven't consumed frequently enough for there to be a large enough diffusion gradient of THC-COOH in the blood to diffuse into the new hair.

What you feel has no part in this... it is what it is... if you had enough its already locked into your hair (any of the hair on your body) ready to be detected. How much you consumed is possibly less important than how strong it was, as that can vary significantly.

I need to ask... what "random" test gives you 30 days advance warning you will be taking it?

Well, I passed. Also, it was for an internship at a nuclear facility.

Congratulations. Intern ships often turn into jobs and a job at a nuclear facility is a nice job to have. They probably do a bunch of drug testing don't they? Might be a good time to kick any habits you have.