[Grammar] She has learnt/has been learning to drive for two months.

[tedmc]

I think it is also natural for them to take their test if it is a common test.

 

[kadioguy]

Peter and Paul are both taking their theory tests tomorrow.

That is perfectly acceptable an (to me, natural) if they are taking their tests along with other people in the same room.

What does the "an" mean?

 

[kadioguy]

I think it is also natural for them to take their test if it is a common test.

What do you mean by "a common test"?
(Are you implying that some tests are special? ;-))

 

[tedmc]

What do you mean by "a common test"?
(Are you implying that some tests are special? ;-))

Common as in being the same or identical, not ordinary.