Using JUnit to test a main method that requires simulation of keyboard input with an input stream?

Question

Let\'s suppose I have a program with a main method that uses the java.util.Scanner class to receive user input.

import java.util.Scanner;

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Answer 1

The System Rules library provides JUnit rules for such tests. Additionally you should use a parameterized test.

Answer 2

You can redirect System.out, System.in, and System.err like this:

System.setOut(new PrintStream(new FileOutputStream("output")));

System.setErr(new PrintStream(new FileOutputStream("error")));

System.setIn(new FileInputStream("input"));

So in you unit test you can setup this redirection and run your class.