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

[Rafael Knuth]

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