no number is correct
all number is correct
refactor test
1A0B case
refactor
0A4B case
refactor, make code more simple
validate number length
validate number size
refactor validate to validator
just one validator object
validator with duplicate number
random answer generator
integration answer generator to game
refactor: extract 4 to numberLength variable
refactor: extract answer result
guess history
add game controller for output
number from controller
move history responsibility to controller