Jim Bowes delivered the short version of his Introduction to Agile at WordCamp London in 2017. The talk provides beginners with an intro to the principles underpinning Agile software development, before focusing on the Scrum methodology.
32. USERSTORIES
Independent (of all others)
Negotiable (not a specific contract for features)
Valuable (or vertical)
Estimable (to a good approximation)
Small (so that you can fit several in an iteration)
Testable (in principle, even if there isn’t a test for it yet)