heee
during test, changing lane is very tricky - better get permission from examiner first; otherwise, he/she can easily fail you even there is no car on the lane you switch to.
for example, they will tell you that 'the speed for the other lane is supposed to be faster than the speed of the lane you were originally driving in.' so, if you didn't speed up first even there were no car in the other line, they could fail you; however, if you got your speed up, they might complain you were speeding...