Re: [pdf-devel] time module unit test cases

[gerel]

 > Date: Fri, 18 Apr 2008 20:55:05 +0200
 > From: address@hidden
 > 
 > 
 >     > Passing an invalid object to the function (an invalid pointer) will
 >     > surely cause the application to crash. It is generally not possible in
 >     > C to determine if a pointer is a "valid" one (if it points to
 >     > appropiately allocated _and_ appropriately initialized memory). Even
 >     > if you expect a crash (and test for the presence of a crash in the
 >     > process) you may be dissapointed: the application may survive if the
 >     > garbage contained in the pointer points to a valid memory
 >     > address. So it is not useful to define negative unit tests with
 >     > invalid pointers.
 >     > 
 >     > I hope that helps.
 >     > 
 > 
 >    NULL pointers indeed are invalid and should always be checked on.
 > 
 > I disagree. Anish is talking about expecting a coherent failure
 > behaviour from a function in case you pass an invalid pointer as a
 > parameter. To check for NULL pointers in a function expecting a
 > pointer parameter is a waste of time. Most pointer variables are
 > automatic variables and thus they are not initialized to 0. In that
 > context to check for NULL is like to check for 24.
 > 
 > What makes sense and of course is mandatory is to check for a NULL
 > pointer after calling a function that _explicitly_ set the return
 > value as NULL when there is a failure or some other condition.


Let's use an example so I get your point.

##

/*
 * Test: pdf_list_create_002
 * Description:
 *   Try to create an empty list given a NULL list pointer.
 * Success condition:
 *   Returns PDF_EBADDATA
 */
START_TEST (pdf_list_create_002)
{
  fail_if (pdf_list_create (l_comp, l_disp, 0, NULL) != PDF_EBADDATA);
}
END_TEST

###

Is that unit test useless ? If so, I wasted a long time checking for NULL
pointers and doing those tests. :-/ (dumb me)


-gerel