How to send input to System.console.readLine(...) in Junit?

Question

I have a main method I'd like to test.

I'm just wondering how to pass what the console.readLine(...) and console.readLine(...) is expecting from my Junit test - without refactoring main(...) - I'm using JMockit if that would be of use here - i.e. mocking out the System.console()?.

class MyClass {
    public static void main(String[] args) {
        Console console = System.console();

        String username = console.readLine("Enter your username: ");
        char[] newPassword = console.readPassword("Enter your new password: ");

        ...
    }
}

class MyJunitTest {
    @Test
    public void test() {
        MyClass.main(null);
        // here I'd just like to pass the username and password to the console?
    }
}

There's a lot more going on in main(...) than just this, I need to get past this first in order to test the rest of it. — user2586917, Jun 04 '14 at 13:34
Why do you need to pass console.readLine(...) to main method ? Anyway Console object is created inside main method. — Ninad Pingale, Jun 04 '14 at 13:35
I believe this problem has been solved here: [JUnit testing with simulated user input](http://stackoverflow.com/questions/6415728/junit-testing-with-simulated-user-input). Simply set your own input stream for System.in. — mttdbrd, Jun 04 '14 at 13:40
Thanks @mttdbrd - I actually ended up using JMockit to do this, see my answer below. — user2586917, Jun 04 '14 at 13:50
The best answer is "don't do that". Break the API apart so that you can directly call the code that needs that input from your unit test. — chrylis -cautiouslyoptimistic-, Jun 04 '14 at 13:59

score 2 · Accepted Answer · answered Jun 04 '14 at 13:50

I got this to work using JMockit to mock the Console class:

  @Test
  public void test(
      @Mocked final System systemMock,
      @Mocked final Console consoleMock) {
    new NonStrictExpectations() {
      {
        System.console();
        result = consoleMock;

        consoleMock.readLine(anyString);
        result = "aUsername";

        consoleMock.readPassword(anyString);
        result = "aPassword";
      }
    };

    MyClass.main(null);
  }

How to send input to System.console.readLine(...) in Junit?

1 Answers1