Green : playing all 'tails' will result in a draw
Red : first player plays different, she must win
Green
Refactor : extract constant
Red : second player plays different, she must win
Green
Red : third player plays different, she must win
Green
Refactor : manually curry a function
Red : add a fourth player trying to find a pattern
Green
Refactor : change a condition in a nested if to search a pattern
Refactor : pattern found, let's see the end of the story
Add more tests to make the pattern clearer