Depends on the idea and how you plan to market it. Some you really can't test. If you plan on advertising, easy. Just run a very small ad campaign and check con

Depends on the idea and how you plan to market it. Some you really can't test. If you plan on advertising, easy. Just run a very small ad campaign and check conversions. Create a landing page that garners interest and asks for the users email and lets them know when the product is finished. http://www.mailboxapp.com http://www.mailboxapp.com was a recent example that started testing the market with no product.