Hanging isn't my area of expertise, but I would imagine that those kind of risks would be present. Ideally, you probably wouldn't do any testing on yourself at all until you were actually ready to commit at that moment, and then the testing could be a preliminary stage in your actual attempt. That way, if your test proved fatal, you would have still achieved your goal, and if it didn't, you could try again on another appropriate occasion. But I know testing things out first is human nature, so at the very least you would want to make sure you had tested and fully understood any knots or mechanisms whilst not on your body, before considering testing them out on your body.
A forum search or look in the megathreads may find more useful advice on this question.
