Re: Universal test flag

I suggest using subroutine constants that are set in a BEGIN block before the module is loaded with use. This way the test mode/debugging code has no performance or memory hit at runtime due to constant folding. Make sure to check with B::Deparse or B::Concise that test mode code was fully removed from the opcode tree, it is very easy to break constant folding. I have a problem with seeing 2-8 parameter debug subroutine calls every 3-6 lines in a CPAN module to enable console printing debugging (as if Perl doesn't have a debugger with a watch window).

Comment on Re: Universal test flag

Replies are listed 'Best First'.
Re^2: Universal test flag by ait (Hermit) on Jul 17, 2012 at 13:17 UTC
Thanks for your comment. Yes, I understand your concern and I second your opinion that print statements for debugging are a bad idea, one of the reasons I looked into using callbacks that could allow the test software to inspect intermediate results within a sub. There are some situations (e.g. "large amount of state data shared among the different steps of a function" see 880089) in which intermediate values inside a sub need to be evaluated, but instead of printing these ase debug statements I have been using a "test point" analogy that I describe here 882331. This allows a your test to diagnose the problem better before firing up the debugger to fix it. Of course many of this situations can be avoided with better design, but in the real world time and budget constraints don't allow for adequate refactoring to fix these design problems. The test point idea was precisely for eliminating all these print-debug statements and move these intermediate values to be evaluated in the test suite instead of reading and making sense of all the verbose debug statements.	[reply]
Re^3: Universal test flag by bulk88 (Priest) on Jul 17, 2012 at 15:19 UTC
I dont see Using Test-Point Callbacks for Automated Diagnostics in Testing as being any more efficient than a print statement since multiple arguments of lexicals are still evaluated and copied if the branch is taken and those instructions will not be removed, although they wont execute, with debugging mode off. The only advantage I see of Using Test-Point Callbacks for Automated Diagnostics in Testing is that errors can be discovered automatically with code, rather than the programmer looking for a needle in a haystack wrong value in a mile of debug channel.	[reply]
Re^4: Universal test flag by ait (Hermit) on Jul 17, 2012 at 16:06 UTC
Exactly! That is precisely the idea: to give a more intelligible diagnostic message instead of having to go through millions of debug messages. Whilst the general consensus that the smallest testable unit is a sub, in many real world applications this is simply not the case. A lot of business code has a lot of state data shared in long subroutines. They are always room for refactoring but in the mean time, you need to provide mechanisms to test this code the best you can.	[reply]