The concept of the Testing Playbook has been recently added to the list of possible tools in your Context-Driven toolset. The Playbook has been described as being similar to the list of plays that a football team would prepare before a big game. The plays in the playbook are how the team plans to play the game, but everyone knows that the coach might make different decisions when the actual game happens. Football in this case refers to American football. I don't know, but soccer or rugby might have similar concepts.
Not enough has been written about this.
What are the things someone might include in their Testing Playbook? Why include those things?