[FIXED] Java/JUnit - How does testPrintMessage() get called?

Issue

In the following code, how does method testPrintMessage() get called? I dont see any code explicitly calling it.

TestRunner.java

import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;

public class TestRunner {
   public static void main(String[] args) {
      Result result = JUnitCore.runClasses(TestJunit.class);
      for (Failure failure : result.getFailures()) {
         System.out.println(failure.toString());
      }
      System.out.println(result.wasSuccessful());
   }
}

TestJunit.java

import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class TestJunit {

   String message = "Hello World";
   MessageUtil messageUtil = new MessageUtil(message);

   @Test
   public void testPrintMessage() {
      assertEquals(message,messageUtil.printMessage());
   }
}

MessageUtil.java

public class MessageUtil {

   private String message;

   //Constructor
   //@param message to be printed
   public MessageUtil(String message){
      this.message = message;
   }

   // prints the message
   public String printMessage(){
      System.out.println(message);
      return message;
   }
}

I tested this code in Eclipse and it works:

Hello World
true

Solution

When JUnitCore.runClasses(TestJunit.class) gets called, JUnit finds all public methods annotated with @Test and invokes them reflectively.

Answered By - Peter Niederwieser
Answer Checked By - Gilberto Lyons (JavaFixing Admin)