command line - Testing console based applications/programs - Java

Question

All,

I have written a PhoneBook application in Java that is command line based. The application basically asks for some details of user like Name, Age, Address and phone numbers and stores them in a file. Other operations involve looking up PhoneBook by name, phone number etc. All the details are entered through console.

I am trying to write JUnit test cases for each of the functionalities that I have implemented but not able to figure out how to redirect System.in in the implementation code to something in my JUnit test methods that would supply those values when my actual code stops for user input?

Example:

My implementation code has:

BufferedReader is = new BufferedReader (new InputStreamReader(System.in));
System.out.println("Please enter your name:");
String name = is.readLine();             // My test cases stop at this line. How can I pass command line values i.e. redirect System.in to my test based values?

Hope it makes sense

Answer 1

Why not write your application to take a Reader as input? That way, you can easily replace an InputStreamReader(System.in) with a FileReader(testFile)

public class Processor {
    void processInput(Reader r){ ... }
}

And then two instances:

Processor live = new Processor(new InputStreamReader(System.in));
Processor test = new Processor(new FileReader("C:/tmp/tests.txt");

Getting used to coding to an interface will bring great benefits in almost every aspect of your programs!

Note also that a Reader is the idiomatic way to process character-based input in Java programs. InputStreams should be reserved for raw byte-level processing.