I detest it when best practices from the tech industry are poached. The fail fast and fail often model only works when there are no planned or expected results.  Even the input models have to be variable. 
The users have to accept that the final product whether they get what they expected is the product and then decide whether to use it.
To quote Mick: " You don't always get what you want to but if you try real hard, you get what you need".