Testing loop statements

A design question: which type of loop do you need? a definite loop ("for") or an indefinite loop ("while")

For any loop control structure, you need to consider 3 basic cases

the loop does NOT execute its body at all
the loop body executes exactly one time
the loop body executes more than one time

None of these are necessarily error conditions, but you should make sure the code has been tested.

Can the first case happen with a "for" loop? Yes, it is possible.

     for i in range(num):
        #body

If num has the value 0, the body will never be executed.

     for line in infile:
       # body

If the file is empty, the body will never be executed.

Another thing to check on a loop is does it start and stop at the right time?

if the body should not execute at all, does that happen?
does the body get executed one time more or one time fewer than it should? (called "off by one" error)
does the loop stop at ALL? (an infinite loop!)

A question to check: are the correct statements inside the loop and are the correct statements outside the loop? In other words, are the statements being repeated the ones that should be?