[Tutor] Unit testing in Python (3.3.0) for beginners

[Mark Lawrence]

On 08/12/2013 10:22, Rafael Knuth wrote:
> Hey there,
>
> I struggle to understand what unit testing specifically means in
> practice and how to actually write unit tests for my code (my gut is
> telling me that it's a fairly important concept to understand).
>
> Over the last few days I learned how to write and work with classes, I
> learned quite a lot about functions, nested loops and I currently walk
> through every program in the Python.org wiki "Simple Programs"
> https://wiki.python.org/moin/SimplePrograms ... and here's the unit
> test program they provide:
>
> import unittest
> def median(pool):
>      copy = sorted(pool)
>      size = len(copy)
>      if size % 2 == 1:
>          return copy[(size - 1) / 2]
>      else:
>          return (copy[size/2 - 1] + copy[size/2]) / 2
> class TestMedian(unittest.TestCase):
>      def testMedian(self):
>          self.failUnlessEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7)
> if __name__ == '__main__':
>      unittest.main()
>
> Also, I went through the "Beginning Test-Driven Development in Python"
> http://net.tutsplus.com/tutorials/python-tutorials/test-driven-development-in-python/
> but I have to admit I still don't fully understand how unit tests work
> in practice and how to write my own unit tests.
>
> As it turned out over the last few weeks, the best modus operandi for
> me as an absolute beginner is to grab a small program, take it apart
> in the first place, understand how each component works through trial
> & error, then put all those pieces together and then I kind of get the
> big picture. Once I "get  it" I practice as much as possible to
> memorize what I just learned and *then* I start readying as many
> blogs, tutorials etc. as possible to deepen my understanding (I
> frankly find most tutorials & blogs too complex and confusing from a
> beginner's viewpoint, and I learn faster by taking code apart and
> learning through trial & error in the first place). So, what I am
> specifically searching for is a very simple code sample which I can
> take apart and iterate through each component, and I was wondering if
> you are aware of resources that might be helpful?
>
> My understanding of unit testing is that I have to embed my code into
> a test and then I have to define conditions under which my code is
> supposed to fail and pass. Is that assumption correct?
>
> I am a bit lost & confused here .. any help & hing is highly appreciated!
>
> Thank you & all the best,
>
> Raf

Two pieces of advice from me, one don't overthink it, two why not look 
at Python's own unit tests?  On my Windows 7 box they're here 
C:\Python33\Lib\test, I'm sure you can find the equivalent on your own 
machine.  Perhaps pick some builtin functions and modules from the 
standard library that you've used, and see how the core developers go 
about testing them.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence