import junit.framework.TestCase;

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

public class HelloWorldTest extends TestCase {

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

    public void testHelloWorld() {
        // [Arrange] Capture "Standard I/O" System output:
        final PrintStream oldSystemOut = System.out;
        final ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        final PrintStream printStream = new PrintStream(byteArrayOutputStream);
        System.setOut(printStream);
        try {

            // [Act] Code Under Test:
            main(new String[0]);

        } finally {
            System.setOut(oldSystemOut);
            printStream.close();
        }

        // [Assert]
        assertEquals("Hello World!" + System.lineSeparator(), byteArrayOutputStream.toString());
    }

}