TDD for Java命令行程序和嵌套的readLine（）

Basically, I'm writing a Java Command-line application which accept parameter from user by readLine. Ex, if the user press "1" it will ask which book the user wants to check out, the user can press the number of the book by "1" or "2" ... So, the application accepts user parameter two times. And I'm trying to use TDD to test the application alongside as well. Basically, I'm writing a Java Command-line appl