This will bite you if you use Guava's ImmutableX types.

jmock_abstract_collecitons.java

public class AppTest
{
    @Rule public JUnitRuleMockery context = new JUnitRuleMockery();

    public static interface ColGetter {
        public abstract Col get();
    }

    public static interface NonColGetter {
        public abstract NonCol get();
    }

    @Test
    public void cantDoCollection() {
        final ColGetter icut = context.mock(ColGetter.class);

        context.checking(new Expectations() {{
            oneOf(icut).get();
            will(returnValue(null));
        }});

        icut.get();
    }

    @Test
    public void canDoNonCollection() {
        final NonColGetter icut = context.mock(NonColGetter.class);

        context.checking(new Expectations() {{
            oneOf(icut).get();
            will(returnValue(null));
        }});

        icut.get();
    }

    public abstract class Col implements Collection {

    }

    public abstract class NonCol {

    }
}