Dear moderators,

We already know that the rule of question tag is that a negative sentence is turned into a positive one and vice versa.

But are there any cases where we can use a positive tag even the sentence is positive,too, or vice versa i.e a negative tag with a negative sentence?
I know that this is possible when the sentences expresses ,for example, an order that must be carried out as the one below.
Father to son: "You will buy the bread today, will you?"

I would appreciate it if you could elaborate on this.

Swan* describes this kind of question tag as 'same-way' question tags, with this example: You're getting married, are you?.

He states:

Non-negative question tags are quite common after affirmative sentences. These are often used as responses to something that has been said....The speaker repeats what he/she has just heard or learnt, and uses the tag to express interest, surprise, concern or some other reaction:

So you're getting married, are you? How nice.
So she thinks sh's going to become a doctor, does she? Well, well.
You think you're funny, do you?

'Same-way' tags can be used to ask questions. In this structure, we use the main sentence to make a guess, and then ask (in the tag) if it was correct.

Your mother's at home, is she?
You can eat shellfish, can you?
This is the last bus, is it?

[i]I'll...shall I?[/] can be used to make offers

[i]I'll hold that for you, shall I?
_______

My feeling is that these same-way question tags are used more in British English than in American English.

In addition, certainly in American English, they often express hostility or present a challenge:

So you think you're going to marry my daughter, do you?

You want me to do your work for you, do you?

Jack said that about me, did he? We'll, he'd better apologize!
_______
*Practical English Usage, by Michael Swan. Oxford 2005

Thank you, Rachel.
But what if the question tag is an item of an exam is it acceptable to answer it using same-way structure or I have to answer it in the normal way? And when can we use both?

Unless there are special instructions,I would go with the normal way.

I truly appreciate this, Rachel.
Thank you so much.