[fpc-pascal] FPCUnit article/tutorial online.
dezobec at tin.it
Mon Oct 10 20:56:37 CEST 2005
L505 ha scritto:
>Since I don't exactly know what test frameworks are, even after reading about them for the
>past few years, I'm going to ask some risky questions. This is not a flame thrower attempt
>at the test framework advocates, I'm just trying to understand what exactly they do, from a
>"newbie to test frameworks" perspective.
I did not understand the full benefits of unit tests till I've tried them.
And it took a lot to get accustomed to them.
>Do test frameworks
> -cause you to spend lots of time writing test frameworks instead of program code?
The function of the xUnit testing framework is to let you write tests
faster and with less effort. It's a matter of personal development
habits and preferences of course, but the greatest benefit of unit
testing I've experienced was the reduction of time spent with the
debugger (I still don't know how to use it effectively with Free Pascal
and in Lazarus I usually keep it disabled :) A failing test usually
leads me directly to the problem. The safety net provided by the tests,
written at the same time as I write the code gives me courage to do the
refactoring that I find usefull when I review the code to improve the
design, or the changes that I need to apply when I do some profiling.
It assures me I've not introduced collateral damage.
> -even apply to languages with compilers and strong typing?
I has nothing to do with strong typing IMHO, I love strong typing but it
does not solve all my problems. I'm not a perfect programmer, I'm quite
successful in making mistakes and I need to be sure that a piece of code
does exactly what I thought it should do, without making assumptions and
discover the problem later, when the code has been used in other higher
level functions or frameworks
> -cause you to write your programs to conform to the test framework, instead of the program
Not all kind of code can benefit from unit testing, it's no use in my
opinion to try to test the GUI code, and it's difficult to test some
parts of web or db applications.
But in my case, when I'm doing unit testing of non visual code in more
complex frameworks and I find a class that is difficult to test in
isolation, I've noticed that in most occasions this is due to some flaw
in my design, often the classes proved to be too tightly coupled or had
a wrong interface. So, from my experience, writing tests has the side
effect to improve the design of my code.
> -have any actual statistics of success?
The Free Pascal Compiler is the best example of the success of testing,
have you seen how many test have our compiler gods put in place in their
testing suite? It's not fpcunit but the effect is the same. It was the
first think I've noticed when I checked out the code from cvs the first
time. Then I've noticed that each time a bug was found it was pinned
down in a test to prevent it to emerge again, and I've begin to learn
some other good tricks from them.
> -have popularity statistics that prove they are popular (in the Delphi community) as stated
>in the article?
I'm quite sure that the folks at Borland don't do a lot of unit testing
;) after all DUnit and NUnit are open source products :), but yes, in
the open source Delphi community they are quite popular, see the Jedi
JCL project that uses DUnit for example:
The developers that took over the InstantObjects framework development
are now successfully using FPCUnit to begin to understand the complex IO
framework, pinpointing the code to be able to do some changes safely and
maybe to pave the way for the Lazarus port. (See
The Mono project is successfully using NUnit too.
> -have any real world examples of how they helped personX fix problemY in significantly less
It's not about fixing a problem in my experience. It's about maintaining
the same level of productivity when the system grows. To be able to do
fearless refactoring in the phase of reviewing the code when
discovering some "bad smells", to be able to improve the design.
I find it difficult to begin some large refactoring without a solid base
of tests in place. When I publish some code I prefer to thoroughly test
it before and when I submit a bug report I found practical to provide a
failing test that isolates it. Unit Tests are not a panacea to all the
problems, but they make my work easier. It helped me to drastically
reduce the time I've spent debugging. It took some time and effort to
learn to write good tests but for me it was a good investment. By doing
the tests as I write the code I've learned to spend less time in
developing good tests (it's like mowing a lawn, when the grass is small
it's easier). It keeps my productivity stable even when the code is
getting complex and it even helps me to isolate a reported bug in my
code. Now I'm really having fun in coding.
>Hoping the answers are no, yes, no yes, yes, yes.
The answer was quite more articulated and subjective :) there's no use
in saying that unit testing is good for everyone. If the developer
enjoys doing it, as I do, it's a good thing in my opinion. But I'm
convinced that there's not one true way of writing good quality
software, every one has to find the one best suited to his needs.
More information about the fpc-pascal