How to validate a startup idea before writing a line of code

In 1999, three Cambridge graduates set up a stall at a jazz festival in London and sold smoothies they had made themselves. Above the stall hung a sign asking whether they should quit their jobs to make smoothies full time. Customers voted by dropping their empty bottles into a bin marked “yes” or one marked “no”, as Business Insider recounted. The “yes” bin won, and Innocent Drinks was born. It…