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class Helper {
  def help = "helpfulResult"
  def helpWith(problem: String) = problem + " whatever help for String problem"
  def helpWith(problem: int) = problem + " whatever help for int problem"
}

class Cut(helper: Helper) {
  def doWork: String = {
    helper.help + " processed"
  }

  def doWork(problem: String): String = {
    helper.helpWith(problem) + " str processed"
  }

  def doWork(problem: int): String = {
    helper.helpWith(problem) + " int processed"
  }
}

import junit.framework.TestCase
import junit.framework.Assert._

import org.jmock.Mockery
import org.jmock.lib.legacy.ClassImposteriser
import net.xofar.jiva.util.mock.SExpectations
import org.jmock.Expectations._

class TestCut extends TestCase {

  val context = new Mockery() {
    {
      // we want to be able to mock classes
      setImposteriser(ClassImposteriser.INSTANCE);
    }
  };

  def test1 = {
    // create the mock
    val helper = (context.mock(classOf[Helper])).asInstanceOf[Helper]
    
    // setup mock return values
    val noOpHelpReturn = "mockHelp"
    val strHelpReturn = "mockHelp stringResult"
    val intHelpReturn = "mockHelp intResult"
    
    // set Expectations
    context.checking(
      new SExpectations() {{  
        one(helper).help
        will(returnValue(noOpHelpReturn));
        
        exactly(1).of(helper).helpWith(withArg(any(classOf[String])))
        will(returnValue(strHelpReturn));
        
        atLeast(1).of(helper).helpWith(withArg(any(classOf[int])))
        will(returnValue(intHelpReturn));
      } 
      }) 
 
    // setup the class under test with the mock
    val cut = new Cut(helper)
    
    
    // exercise the class under test
    // and verify results 
    val result = cut.doWork
    assertEquals(result, noOpHelpReturn + " processed")

    val result2 = cut.doWork("task")
    assertEquals(result2, strHelpReturn + " str processed")
 
    val result3 = cut.doWork(3)
    assertEquals(result3, intHelpReturn + " int processed")
 
    // make sure that the expectations on the mock were satisfied
    context.assertIsSatisfied
  }
}

• We set up Expectations using something called SExpectations.
• We specify method paramater expectations using a method called withArg, as opposed to the more familiar with method provided by JMock

package net.xofar.jiva.util.mock;

import org.hamcrest.Matcher;
import org.jmock.Expectations;

public class SExpectations extends Expectations {
  public <T> T withArg(Matcher<T> matcher) {
    return super.with(matcher);
  }
}

• To work with JMock, you need to use Scala with the -Ygenerics and -target:jvm-1.5 options.
  
• I used JUnit 3 for my Scala unit tests because the Scala Eclipse plugin does not quite support annotations. The standalone/command-line version of Scala supports annotations just fine, so it should be very possible to use JMock/JUnit 4 with Scala
• I suppose I could have used MockObjectTestCase as a base class for my Tests. I just wanted to have more control over things as I worked through the Scala/JMock integration
• I used the CGLib based Legacy ClassImposteriser because I needed to mock system classes for testing Jiva code
• Versions used - Scala: 2.6.0, JMock: 2.4.0