Although this sounds like a sure-fire system, the odds are that price will wiggle up and down enough to hit a 10 pip stoploss far more often than a 30 pip take profit.
If you want to simplify the test (DEMO ACCOUNT ONLY!!!), skip the coin toss and open short and long positions at the same time using 10 pip stops and 30 pip take profit number.
Do 10 sets of trades like this. Pick the pairs with the narrowest spread. Wait a few hours, and check your results. You might come out ahead, but overall, I'll wager than you usually end up in the red.
Of course, there's only one way to find out for sure.
