The runtest script uses random ordering of tests and assigns a random seed 
to the random number generator at the start. However, there are several 
places (most in mpmath) where the seed is reset. This essential guarantees 
that the tests run *after* that reset are always run in the same order, 
regardless of the seed that the testing process started with.

>>> def foo():
...  import random
...  random.seed(0)
...
>>> import random
>>> random.seed(0)
>>> random.random()
0.84442185152504812
>>> foo() # this resets the seed so we get the same random number again
>>> random.random()
0.84442185152504812


I've removed this misuse of seed in sympy's code (and made a patch to 
compatibility to allow the same seed to generate the same randint, etc..., 
under different versions of python at 
https://github.com/sympy/sympy/pull/1310) but am not sure what to do about 
mpmath. Perhaps the test runner could be patched to getstate before running 
mpmath and setstate afterwards?

/c

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