I actually talked to someone about this the other day, as I personally have never tested my own speed. My friend told me it just depends on the company and the type of work they're doing. So say, you're going for this one job at a Medical Insurance office typing up claims, its best that you type the speed you're reading (ideally). I was looking at this one job that was looking for 60+ wpm, which is why I was asking my friend about it. She told me I prolly could easily go faster than that. *shrugs* But here's my opinion on your question (sorry about my rambling).
"Random basic words, like the program I used?"
Personally, I think this works best because it tests your reading skills as well and to make sure you're not assuming anything either.
"A paragraph of words in proper sentence structure?"
Not too bad, but like I said... I think you would assume a little too much which could make you open to mistakes and such.
"Your typing speed when you type from your own mind?"
Personally, I think everyone types faster when from their mind. So I don't know about that...
"Or random words, some of which you have never seen or used?"
I think that pushes the whole typing speed too far.