Walk forward test

Q: We all know that future performance does not resemble past performance. If I have found a good trading model for a stock, should I perform some walk forward test? If yes, how can I reserve some price data (which has never been seen by the model) for the walk forward test? Technically, how can I conduct the test?
A: Our models are purely statistical. We took every care to avoid any chance of using forward info or any other technique, which could compromise optimization results in live trading. One could expect that the models will perform in future approximately same as they did in the past. At least as far as fundamental statistics will not completely change for given symbol.