Running Junit on Standard out from Hello World

I'm trying to run junit on a "Standard" Hello World! program. Here's my program:

public class HelloWorld{
    public static void main (String[] argv)
    {
        System.out.println("Hello World!");
    }
}

What I want to do is call this file and run assertEquals("Hello, World!", output); on it. I've tried a few different things with no success. The first was installing System-Rules by adding it to a lib folder, then importingimport static org.junit.contrib.java.lang.system.TextFromStandardInputStream.*; In this script:

import static org.junit.Assert.*;

import org.junit.Test;
import static org.junit.contrib.java.lang.system.TextFromStandardInputStream.*;

public void HelloWorldTest {
    @Rule
    public final SystemOutRule systemOutRule = new SystemOutRule().enableLog();

    @Test
    public void writesTextToSystemOut() {

        assertEquals("hello world", systemOutRule.getLog());
    }
}

This script threw a bunch of errors and ultimately failed. The other thing I tried was extending class Hello World, but that didn't work either. My ultimate goal here is to be able to run a test on the file HelloWorld.java with no modification to the HelloWorld.java file.

I much appreciate the help!