(red)  Write failing test => Version5UuidSetter#set_uuid does not set
uuid if object is not blank
(green) Make test pass => Version5UuidSetter#set_uuid does not set
uuid if object is not blank
(green) Write failing test => Version5UuidSetter#set_uuid sets uuid
to object if object uuid is blank
(green) Make test pass => Version5UuidSetter#set_uuid sets uuid to
object if object uuid is blank