Subj : Re: Not debugging?
To   : comp.programming,comp.lang.java.programmer,comp.lang.lisp
From : Phlip
Date : Fri Aug 26 2005 07:31 am

Peter Ammon wrote:

> I've been waiting for someone to make this claim about unit testing. Guess 
> I'll pick on you :)

Oh goody 'cause I didn't claim it. [I think.]

> I don't believe that unit testing eliminates debugging.  I'll give a real 
> life example.

Some TDD authors prevaricate and say "/virtually/ bug free". My emphasis. I 
prefer to prevaricate more accurately and usefully.

TDD produces bug-resistant code, with reduced the odds of long bug hunts. 
The kind that typically require debugging and/or trace statements.

> We had a bug where an update to our library disabled some features of a 
> client program.  After some investigating, it was determined that the 
> client program was doing this:
>
> if (library_version == 3)
>
> instead of this:
>
> if (library_version >= 3)
>
> Our fix for this bug was to detect the client and report 3 for the version 
> if the client was the offending program, and otherwise report the true 
> version.

TDD works in tiny steps. Upgrading a library is a big step (and another 
"legacy" situation). Fortunately, your tests let you roll back to the 
previous library version for frequent sanity checks (and emergency 
releases), until you debug the situation.

> be approached in the test-first "no debugging" philosophy.

There is no test-first "no debugging" philosophy. Test cases make an 
exquisite platform for debugging. For example, in VB[A] I use Debug.Assert 
in a test case, and failure raises the debugger. Then I move the current 
execution point back to the called method, step inside it, fix the code to 
pass the test, and resume running the remaining tests.

Without TDD, this is the Unholiest of Unholies - programming in the debugger 
to generate spaghetti code. With TDD, it's nothing more than leveraging your 
tools effectively.

When people use TDD, they generally report surprise that the incidences of 
_punitive_ debugging, with absolutely no other recourse, go way down. And 
some teams (in greenfield projects with user-level code) indeed never turn 
on their debugger, and code for years without it.

-- 
  Phlip
  http://www.greencheese.org/ZeekLand  <-- NOT a blog!!!

.