### Question:
ExecutorManager { public void clearTasks() { MemoryQueue.getInstance().clear(); TaskRouter.getInstance().clear(); } private  ExecutorManager(); static ExecutorManager getInstance(); boolean pullMemTask(); boolean pullDBTask(); void clearTasks();  }### Answer:
@Test public void testClearTasks() { PowerMockito.mockStatic(TaskRouter.class); TaskRouter taskRouter = Mockito.mock(TaskRouter.class); Mockito.when(TaskRouter.getInstance()).thenReturn(taskRouter); ExecutorManager.getInstance().clearTasks(); Mockito.verify(taskRouter).clear(); Mockito.verify(memoryQueue).clear(); }