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Re: Question re testing constructor

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Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> wrote in
news:s8adnYgtFe-Nq0PTnZ2dnUVZ_oGdnZ2d@posted.palinacquisition: 

> On 12/6/11 7:14 AM, Novice wrote:
>> [...]
>> I've satisfied myself via googling that it makes sense to test
>> constructors if they do something that might fail or if they can
>> throw exceptions. The constructor in question can throw exceptions so
>> I'm trying to write some test cases for it. I've got cases that cause
>> each of the exceptions to be thrown but I'm having a bit of a problem
>> with what seemed like the easiest test of all: existence.
>>
>> It seems to me - correct me if I'm wrong - that I can easily test to
>> make sure the constructor actually built SOMETHING by testing the
>> object against null. [...]
> 
> Sorry.  You're wrong.  :)  Simply executing the next statement
> following the use of "new" is all the confirmation you need "to make
> sure the constructor actually built SOMETHING".  Testing against
> "null" yields no additional information.
> 
> As "markspace" says, the "new" operator always returns a new object. 
> The only way for it to fail is to throw an exception, in which case
> the "new" operator never actually returns per se (and so any code that
> follows it is reachable only the case where it returns a non-null
> value). 
> 
> So you don't need to test for existence.  Checking for a "null" return
> value will needlessly verify that "new" succeeded, but cannot detect 
> failure because that's not how "new" reports a failure.  Just test the
> exceptions as you're already doing.
> 

Thanks Pete! You and markspace have clarified things for me and saved me 
some work to boot since I can now delete the existence tests.


-- 
Novice

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Thread

Question re testing constructor Novice <novice@example..com> - 2011-12-06 15:14 +0000
  Re: Question re testing constructor markspace <-@.> - 2011-12-06 07:23 -0800
    Re: Question re testing constructor Novice <novice@example..com> - 2011-12-06 17:17 +0000
    Re: Question re testing constructor Tom Anderson <twic@urchin.earth.li> - 2011-12-06 21:25 +0000
    Re: Question re testing constructor Ian Shef <invalid@avoiding.spam> - 2011-12-07 00:29 +0000
      Re: Question re testing constructor Patricia Shanahan <pats@acm.org> - 2011-12-06 19:28 -0800
      Re: Question re testing constructor Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-12-06 22:57 -0600
      Re: Question re testing constructor Lew <lewbloch@gmail.com> - 2011-12-07 07:12 -0800
      Re: Question re testing constructor Lew <lewbloch@gmail.com> - 2011-12-07 07:14 -0800
        Re: Question re testing constructor Ian Shef <invalid@avoiding.spam> - 2011-12-07 15:59 +0000
          Re: Question re testing constructor Ian Shef <invalid@avoiding.spam> - 2011-12-08 19:19 +0000
      Re: Question re testing constructor ilAn <idonot@wantspam.net> - 2011-12-07 20:41 +0200
  Re: Question re testing constructor Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-12-06 07:34 -0800
    Re: Question re testing constructor Novice <novice@example..com> - 2011-12-06 17:15 +0000
  Re: Question re testing constructor Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2011-12-06 09:49 -0800
  Re: Question re testing constructor Roedy Green <see_website@mindprod.com.invalid> - 2011-12-06 16:40 -0800
  Re: Question re testing constructor Henk van Voorthuijsen <voorth@xs4all.nl> - 2011-12-07 00:33 -0800

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