Might help to analyze your fears. Why are you anxious & what's the worst that will happen if all your fears come true? In reality, you could handle whatever that was. You'd treat it as a learning experience & move one (whether that might be failing a test, disappointing youself, etc.)
And, any bookmaker would give 100 to 1 odds that none of those fears will ever cojme true (except the internet connection one). You are amazing on tests, one of the smartest people I know and you will still be if you let that stress go and relax!
Or chillax as they say around here.
You could perhaps write yourself some affirmations/guided meditations on having anxiety-free testing experiences.