code: @Test public void updateShouldBeAbleToUpdateDescriptionOnly(){
    UpdateTaskPayload updateTaskPayload=TaskPayloadBuilder.update().withTaskId("taskId").withDescription("new description").build();
    TaskImpl task=new TaskImpl();
    task.setAssignee("user");
    doReturn(task).when(taskRuntime).task("taskId");
    TaskQuery taskQuery=mock(TaskQuery.class);
    given(taskQuery.taskId("taskId")).willReturn(taskQuery);
    given(taskService.createTaskQuery()).willReturn(taskQuery);
    Task internalTask=mock(Task.class);
    given(taskQuery.singleResult()).willReturn(internalTask);
    taskRuntime.update(updateTaskPayload);
    verify(internalTask).setDescription("new description");
    verifyNoMoreInteractions(internalTask);
  }
  