In JMockit throw exception for a method

Question

Apologies, It may sound a duplicate question.

After googling it I tried to use: result = new Exception(); but had no luck.

MainClass

public class DemoClass
{
    public void processMessage(String message)
    {
        System.out.println("Inside process method. processing message: " + message);
        if (message.isEmpty())
        {
            new IllegalArgumentException();
        }
    }

    public void retry(String message)
    {
        try
        {
            processMessage(message);
        }
        catch (IllegalArgumentException e)
        {
            System.out.println("Reprocessing of process method failed");
            finalMessage(message);
        }
    }

    public void finalMessage(String message)
    {
        System.out.println("Inside finalMessage method. " + message);
    }
}

TestClass

import mockit.Expectations;
import mockit.integration.junit4.JMockit;
import org.junit.Test;
import org.junit.runner.RunWith;

@RunWith(JMockit.class)
public class DemoClassTest
{
    @Test
    public void test() {
        DemoClass demoClass = new DemoClass();
        String message = "Hello World";
        new Expectations() {{

           demoClass.processMessage(message);
           result = new IllegalArgumentException();
           times = 1;

            demoClass.finalMessage(message);
            times = 1;
        }};

        demoClass.retry(message);

    }
}

While running above test class i am getting below error

Inside process method. processing message: Hello World
java.lang.IllegalStateException: **Missing invocation to mocked type at this point; please make sure such invocations appear only after the declaration of a suitable mock field or parameter**

I want to throw error on call of processMessage() method, so that catch block gets executed.

Answer 1

You need to do Partial Mocking

@Test
public void test() {
    DemoClass demoInstance = new DemoClass();

    String message = "Hello World";

    new Expectations(demoInstance) {{
        demoInstance.processMessage(message);
        result = new IllegalArgumentException();
        times = 1;

        demoInstance.finalMessage(message);
        times = 1;
    }};

    demoInstance.retry(message);
}

Notice that we're passing the demoInstance instance to the new Expectations block.