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From Gilles <>
Subject [RNG] Intermittent failure of unit tests (Was: [VOTE][RC5] ...)
Date Fri, 02 Dec 2016 14:11:34 GMT
On Thu, 1 Dec 2016 15:59:24 -0800, Rob Tompkins wrote:
>> On Dec 1, 2016, at 3:32 PM, Gilles <> 
>> wrote:
>> On Thu, 1 Dec 2016 15:29:17 -0800, Rob Tompkins wrote:
>>> Vote: -1 mainly for license,
>> Which files?
>>> but there’s the following as well.
>>> I just ran “mvn clean test" with java 1.7.0_60 on OS X 10.12.1 and
>>> got the following test failure (note that it seems to be
>>> intermittent):
>> Cf. 
>> <>
> I don’t know what to do here. On one hand it really feels like our
> builds should be deterministic, but on the other hand you need to 
> need
> to exercise the code fully in your unit tests. I’m really at odds 
> with
> myself, but I think I lean towards determinism.

As with other issues discussed on this list, this one is not going
to be solved (reasonably, I mean) by tallying "preferences".[1]

It is possible that the unit test's assumption is flawed.[2]
Another possiblity is that the strategy for declaring pass/fail is
too crude; see for example, in the user guide, the output of the
"Dieharder" test suite.[3]


[1] It is easy to select a seed that will make the test deterministic 
     passing.  But it suppresses behavioral diversity, which in turn 
     reveal a potential bug.  This case seems to happen in
[2] Hence the request for review in "RNG-30".
[3] AFAIUC, when a test produces a result that is "close" to the 
     boundary, it is rerun, until a definite conclusion can be reached.

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