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[Python-porting] Control of hash randomization

martin at v.loewis.de martin at v.loewis.de
Sun May 27 10:24:19 CEST 2012 
> That issue is pretty subtle.  The more common case is iterating
> through a set or dict (or a tuple that was sorted by hash, which is
> the most common case for SymPy), and there is some subtle fact about
> the loop that makes the result differ depending on the result of
> iteration.  Quite often, the result is still "correct" (in SymPy, this
> generally means the answer is still mathematically correct), just not
> the same as what the test expected.

But there are standard procedures to deal with that very phenomenon:
use a proper equality function.

People have written tests for years that somehow relied on the order
of keys in a dictionary (an issue in particular for doctest). If you
find a failed assertion, and it involves an equality test, verify that
the comparison uses "normalized" representations of the value. If not,
add the normalization to all related test cases.

Regards,
Martin
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