Should

Tung Quoc wrote:

You should do well on the test. should here expresses advisability or degree of certainty or both? If not both, how to distinguish advisability or degree of certainty in this case? Q

Both. You need more context for clear separation.

I prefer "in".

If someone says to me You should do well in the test, my immediate interpretation is that the speaker considers I have studied well enough. He could say You will do well, but nobody is ever sure.

Also interpretable as advisability, but here I'd be inclined to put it more strongly: You must do well in the test.

To be 100% about the intended meaning of should, you often need more context.
However, I agree with Milky in this case:  should seems to suggest certainty in the sentence. 
If it were advisability, the sentence would normally be worded a little differently.

As regards the prepostition:
I have a sneaking suspicion this may be one of those BE/AmE things:  I'd definitely say 'on the test'.