in tutorials/tutorial2/TicTacToeTests/TicTacToeMocks.swift [34:40]
func build(withListener listener: LoggedInListener) -> LoggedInRouting {
buildCallCount += 1
if let buildHandler = buildHandler {
return buildHandler(listener)
}
fatalError("Function build returns a value that can't be handled with a default value and its handler must be set")
}