JMockit - Can't bind mocked class to tested class

Question

I have an application with 3 layers: App <--> Graph <--> Couchbase

I'm trying to test the GraphConnector by mocking the couchbase layer and "replacing" it with a very basic in-memory graph implementation, using the same approach demonstrated in the JMockit tutorial.

This is my test class (pardon the poor indentation, didn't get the hang of it yet):

public class GraphConnectorTest {
public static final class MockCouchbase extends MockUp<ICouchConnector> {
    private Map<String, CouchEntry> couch;

    @Mock
    public void $clinit() {
        couch = new HashMap<String, CouchEntry>();
    }

    @Mock
    public void put(CouchEntry entry) {
        couch.put(entry.getKey(), entry);
    }

    @Mock
    public CouchEntry get(String key) {
        return couch.get(key);
    }
}

GraphConnectorImpl graph = new GraphConnectorImpl();

@BeforeClass
public static void setUpClass() {
    new MockCouchbase();
}

@Test
public void testPost() throws Exception {
    GraphNode node = new GraphNode(GraphNodeType.DOMAIN, "alon.com");
    graph.post(node);
    GraphNode retNode = graph.getSingleNode(node.getValue(), node.getType());
    assertEquals(node.getValue(), retNode.getValue());
    assertEquals(node.getType(), retNode.getType());    
}
}

And here is my class under test:

public class GraphConnectorImpl implements IGraphConnector {

private static ICouchConnector couch = new CouchConnectorImpl();  // <-- Basic implementation which I don't want the test to execute

@Override
public void post(GraphNode node) {
    CouchEntry entry = new CouchEntry(node.getValue(), JsonDocument.create(node.getValue()));
    couch.put(entry);
}

@Override
public GraphNode getSingleNode(String nodeName, GraphNodeType nodeType) {
    return new GraphNode(nodeType, couch.get(nodeName).getKey());
}
}

For some reason, the class MockCouchbase that I created within the test class isn't automatically bound to the private field ICouchConnector couch of the tested class, as shown in the tutorial. Instead, the real implementation is called, which is obviously undesirable.
If I remove the reference to the real implementation, I just get a good ol' NullPointerException.
I tried playing with the @Tested and @Injectable annotations but to no avail.

Answer 1

Solving my own question.

The problem with the way I wrote the class under test was explicitly invoking the constructor of the real implementation. I'll be surprised if any mocking framework can "bypass" that.

Instead, I should've created a constructor that gets ICouchConnector as one of its arguments, e.g. use dependency injection properly.

public class GraphConnectorImpl implements IGraphConnector {
    private static ICouchConnector couch;

    public GraphConnectorImpl(ICouchConnector connector) {
        couch = connector;
    }
    // Rest of class...
}

JMockit will then attempt to find a constructor that corresponds to the fields annotated @Tested and @Injectable in the test class.

public class GraphConnectorTest {
    @Tested
    GraphConnectorImpl graph;

    @Injectable
    ICouchConnector couch;

    // Rest of class...
}