|Perl: the Markov chain saw|
Test::LectroTest and pseudo random distributionsby pernod (Chaplain)
|on Aug 04, 2005 at 14:40 UTC||Need Help??|
I'm off on a tangent here, so please excuse the off-topicness of this quick example.
How do you test your shuffling or die rolling technique is fair and produces results according to your specifications (say, according to a Gaussing distribution), and isn't biased favouring certain outcomes?
By using Test::LectroTest! Given this trivial implementation of an n-sided die, which returns a number between 1 and the number of sides on your die. Default number of sides is 6.
We then express how we want our die to perform with a Test::LectroTest property that generates a thousand tests with dies with from 1 to 100 sides. We roll the die, and check that the result is legal for this kind of die (eg. within the limits). The second propery generates a thousand six sided dies and rolls each of them once. The results are stored in the the LectroTest controller object with the tcon->label()-call, that automatically spits out the distribution of the roll.
When I run this, I get:
What this means is that the number 2 showed up 18% of the time, 3 17% etc. The numbers don't add up to a 100%, but I presume this is because of rounding in the presentation. In any case, this looks like acceptable behavior for a six sided die to me. I'm sure it's possible to automatically analyze the distribution and build this into the test, but I don't have the time to find out how right now. And please remember that this example was hacked together in a hurry, so I'm sure it can be improved.
I like Test::LectroTest :)
Edit: Removed an erroneous line in the second property.
Retitled by davido from 'OT: Test::LectroTest and pseudo random distributions'.