Mockito mock calling real method implementation when attempting to stub package protected method

Question

I'm trying to stub a method using Mockito 1.8.5, but doing so calls the real method implementation (with "" as parm values) which throws an exception.

package background.internal; //located in trunk/tests/java/background/internal

public class MoveStepTest {

    @Test
    public void testMoveUpdate() {
        final String returnValue = "value";
        final FileAttachmentContainer file = mock(FileAttachmentContainer.class);
        doReturn(returnValue).when(file).moveAttachment(anyString(), anyString(), anyString());
        //this also fails
        //when(file.moveAttachment(anyString(), anyString(), anyString())).thenReturn(returnValue);

        final AttachmentMoveStep move = new AttachmentMoveStep(file);
        final Action moveResult = move.advance(1, mock(Context.class));
        assertEquals(Action.done, moveResult);
    }
}

The method I'm trying to mock looks like this. There are no final method or classes.

package background.internal; //located in trunk/src/background/internal


   public class FileAttachmentContainer {
        String moveAttachment(final String arg1, final String arg2, final String arg3) 
                throws CustomException {
            ...
        }

        String getPersistedValue(final Context context) {
           ...     
        }
    }

And the class I'm passing the mock looks like this:

package background.internal; //located in trunk/src/background/internal
public class AttachmentMoveStep {

    private final FileAttachmentContainer file;

    public AttachmentMoveStep(final FileAttachmentContainer file) {
        this.file = file;        
    }

    public Action advance(final double acceleration, final Context context) {
        try {
            final String attachmentValue = this.file.getPersistedValue(context);
            final String entryId = this.file.moveAttachment(attachmentValue, "attachment", context.getUserName());

            //do some other stuff with entryId
        } catch (CustomException e) {
            e.log(context);
        }    
        return Action.done;
    }
}

What is causing the real implementation to be invoked and how can I prevent it?

Answer 1

The method you are mocking is not accessible to the Mockito code.

Because your test code and your code under test are in the same package, the compiler lets you set up your mock that way, but at runtime, the Mockito library has to try to access moveAttachment, but it's not working in your case. This appears to be a bug or known limitation in Mockito as it should support that case, (and in fact, does support it in most cases).

The easiest thing to do would be to make moveAttachment a public method. If that is not an option, then first question whether you want to even mock it. What happens if the real method gets called?

The last option is to use PowerMock to treat the moveAttachment method as a private method and mock it that way.

Answer 2

I disagree with the accepted response.

I think, you have to provide more details on your environment. I can't reproduce your problem. I write the following code in a maven project :

package background.internal; //located in src/main/java

public class FileAttachmentContainer {
    String moveAttachment(String arg1, String arg2, String arg3) {
        throw new IllegalStateException();
    }

    String getPersistedValue(Context context) {
        throw new IllegalStateException();
    }
}

and

package background.internal;

public class AttachmentMoveStep {

    private FileAttachmentContainer file;

    public AttachmentMoveStep(FileAttachmentContainer file) {
        this.file = file;
    }

    public Action advance(double acceleration, Context context) {
        String attachmentValue = file.getPersistedValue(context);
        file.moveAttachment(attachmentValue, "attachment", context.getUserName());
        return Action.done;
    }
}

and the following test pass

package background.internal; //located in src/test/java

import static org.junit.Assert.assertEquals;
import static org.mockito.Matchers.anyString;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.mock;

import org.junit.Test;

public class MoveStepTest {

    @Test
    public void testMoveUpdate() {
        String returnValue = "value";
        FileAttachmentContainer file = mock(FileAttachmentContainer.class);
        doReturn(returnValue).when(file).moveAttachment(anyString(), anyString(), anyString());
        //this also works
        //when(file.moveAttachment(anyString(), anyString(), anyString())).thenReturn(returnValue);

        AttachmentMoveStep move = new AttachmentMoveStep(file);
        Action moveResult = move.advance(1, mock(Context.class));
        assertEquals(Action.done, moveResult);
    }
}

My project use the following dependencies :

• jdk1.7.0_05
• junit-4.10.jar
• mockito-all-1.9.0.jar
• javassist-3.16.1-GA.jar
• objenesis-1.2.jar
• hamcrest-core-1.1.jar