Four distinct stages make up the Lean Validation Process . Only once you've passed all 4 can you be confident that your product idea is worth developing.

1. Validating the problem. Is this a problem worth solving? If users don't think this is a major problem, your solution won't be appealing.
2. Validating the market. Some users might agree that this is a problem worth solving. But are there enough of them to make up a market for your product?
3. Validating the product. The problem might exist, but does your product actually solve it?
4. Validating willingness to pay. There might be market demand and a great product. But will people actually be willing to reach into their wallets and pay for it?