Mock TaskQuery for Unit test

Below is my service method:

	public Map<String, Object> someMethod() throws Exception {
		
		TaskQuery taskQueryFilterTasks = 
                taskService.createTaskQuery().taskDefinitionKeyIn("some_key");
		return anotherMethod(taskQuery);

	}

I am trying to write Unit test case for this method, for which I need to mock this line:
taskService.createTaskQuery().taskDefinitionKeyIn(“some_key”);
But I am unable to figure out how. Can someone please help?