How can I mock a method in easymock that shall return one of its parameters?

Question

public Object doSomething(Object o); which I want to mock. It should just return its parameter. I tried:

Capture<Object> copyCaptcher = new Capture<Object>(); expect(mock.doSomething(capture(copyCaptcher)))         .andReturn(copyCatcher.getValue()); 

but without success, I get just an AssertionError as java.lang.AssertionError: Nothing captured yet. Any ideas?

Answer 1

Well, the easiest way would be to just use the Capture in the IAnswer implementation... when doing this inline you have to declare it final of course.

MyService mock = createMock(MyService.class);  final Capture<ParamAndReturnType> myCapture = new Capture<ParamAndReturnType>(); expect(mock.someMethod(capture(myCapture))).andAnswer(     new IAnswer<ParamAndReturnType>() {         @Override         public ParamAndReturnType answer() throws Throwable {             return myCapture.getValue();         }     } ); replay(mock) 

This is probably the most exact way, without relying on some context information. This does the trick for me every time.

Answer 2

I was looking for the same behavior, and finally wrote the following :

 import org.easymock.EasyMock; import org.easymock.IAnswer;  /**  * Enable a Captured argument to be answered to an Expectation.  * For example, the Factory interface defines the following  * <pre>  *  CharSequence encode(final CharSequence data);  * </pre>  * For test purpose, we don't need to implement this method, thus it should be mocked.  * <pre>  * final Factory factory = mocks.createMock("factory", Factory.class);  * final ArgumentAnswer<CharSequence> parrot = new ArgumentAnswer<CharSequence>();  * EasyMock.expect(factory.encode(EasyMock.capture(new Capture<CharSequence>()))).andAnswer(parrot).anyTimes();  * </pre>  * Created on 22 juin 2010.  * @author Remi Fouilloux  *  */ public class ArgumentAnswer<T> implements IAnswer<T> {      private final int argumentOffset;      public ArgumentAnswer() {         this(0);     }      public ArgumentAnswer(int offset) {         this.argumentOffset = offset;     }      /**      * {@inheritDoc}      */     @SuppressWarnings("unchecked")     public T answer() throws Throwable {         final Object[] args = EasyMock.getCurrentArguments();         if (args.length < (argumentOffset + 1)) {             throw new IllegalArgumentException("There is no argument at offset " + argumentOffset);         }         return (T) args[argumentOffset];     }  }  

I wrote a quick "how to" in the javadoc of the class.

Hope this helps.