java mockito: is there a way to fake a class that doesnt exists?

I want to fake a new type of class that doesnt exist which implements an interface

is this possible?

for example, i have an interface

public interface Worker {
    boolean execute(Job c);
}

I have a class

public class CompositeWorker implements Worker {
    private List<Worker> childWorkers = new ArrayList<>();
    public List<boolean> execute(Job j){
        return childWorkers.stream().map(w -> w.execute(j)).collect(Collectors.toList());
    }
    public addWorker(Worker worker) {
        childWorkers.add(worker)
    }
}

To test:

public class CompositeWorkerTest {
    private CompositeWorker worker;

    @BeforeMethod
    void setup() {
        MockitoAnnotations.initMocks(this);

        worker = new CompositeWorker();
    }

    @Test
    test_worker() {
         Worker worker_A = mock(Worker.class);
         Worker worker_A = mock(Worker.class);
         Job job = mock(Job.class);
         when(worker_A.execute(job)).thenReturn(true);
         when(worker_B.execute(job)).thenReturn(true);
         worker.add(worker_A);
         worker.add(worker_b);
         List<boolean> results = worker.execute(job);
         //assert results contains true
    }

is there a way to fake/change Worker worker_A = mock(Worker.class); to FakeWorker fakeWorker = mock(FakeWorker.class) which implements Worker but it doesnt actually exists

by NOT exists, i mean there is no definition for:

public class FakeWorker implement Worker 

the reason why I want to mock a different class is because Worker Type is unique

public addWorker(Worker worker) {
    childWorkers = childWorkers.stream().filter(w -> w.getClass() != worker.getClass())
                                                     .collect(Collectors.toList());
    childWorkers.add(worker)
}