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

[Alan Gauld]

On 08/12/13 10:22, Rafael Knuth wrote:

> 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?

That's correct for any kind of unit testing, not just using the
unittest module. Others have shown how to get started with it.
Here are some things to think about when testing.

If you have input parameters that are collections, say a list, then 
always test how the function reacts to an empty list, or a different 
type of collection, say a tuple, or a list of data other than the 
expected type (say you expect a list of numbers and get strings 
instead). And a very large list(some function use recursion
which can break with large data sets) In other words think of
what somebody else using your function might to do it that
could break it.

Similarly with numbers that, say, act as indexes into a list.
Check for negative numbers, zero, small positive numbers,
large numbers, floats, non-numbers

Hopefully that gives some idea of the kinds of things you should
test for. In a real-world project the test code is often bigger 
(sometime much bigger) than the code being tested (although also
much more repetitive!).

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.flickr.com/photos/alangauldphotos