Can you put a live version to test like gowron has done. That way its easier for anyone to evaluate before installing.
Oh, you can get testnet Bitcoins quite easily and deposit into the account as well.
As an Exchange, you can either buy or sell. The Testnet Instance gives you 5K INR test money and allows users to buy from the books or deposit more testnet coins.
You can even withdraw the testnet coins as you need to.
OK; Data for such "Off Market" transactions needs to be returned by your API to be included in the computation.
Or you can simply use the extra amount (instead of asserting net to be zero) and display it as total "withdrawals" or "deposits"