From what I've read it was costing in January about 0.001 BTC to mine 1 tBTC. That's some 40$.
So I guess that a win-win situation could be that you ask for a tBTC loan here and send the proper amount of BTC to an escrow or the lender.
Although that amount will be more than 20$, you'll receive it back (excepting the tx fees) when you finished your tests and send the tBTC back to the lender.