[TIP] Randomizing test order with nose

C. Titus Brown ctb at msu.edu
Thu Apr 23 08:30:57 PDT 2009

On Thu, Apr 23, 2009 at 08:32:33AM -0700, Scott David Daniels wrote:
-> Douglas Philips wrote:
->  > On or about 2009 Apr 22, at 6:36 PM, Scott David Daniels indited:
->  >> There, the simple expedient of subclassing Random by attaching a 
->  >> counter to the root pseudo-random number generator meant that you
->  >> could characterize your position in the random number sequence as
->  >> (_seed, _calls).
->  > ... in previous versions of our attempts to make the PRNG reproducible
->  > we used a counter (and manually  called random() to catch up). It was
->  > very tricky to make sure everyone  had pulled in the right version of
->  > the instrumented random.
->  > Had we planned for that up front we could have forced the bottleneck
->  > necessary. Instead we've found it was just must simpler to seed the
->  > PRNG to captured and known value, when needed....
-> OK, I agree the choke point is a good idea.  However, I ran off
-> and read the random module, and if you can accept a large state,
-> you can certainly use .getstate() and .setstate().  The states are
-> large, so you really want to store them somewhere, rather than retype
-> them (the advantage of the counter -- it can actually be retyped).

I've been thinking about this for a day or two; I looked at
getstate/setstate but saw the same problem as you.

What about just setting the seed yourself, before each test, and then
storing that?  You have the problem of generating a "new" seed, but you
could easily do that by using the time + # of test, or some such.


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