When a value generated by any causes a test to fail inconsistently, it can
be incredibly difficult to track down the failing conditions. In order to
reliably reproduce the problem, you need to be able to get any to repeatedly
produce the same value.
The debug library is in place to enable
revealing the seed that was used for the randomness of generated values. This
means that the seed is not displayed by default, but can be revealed by
instructing debug to output logs for any:
$ DEBUG=any mocha --recursive test/unit/
Thu, 29 Jun 2017 02:13:29 GMT any randomness seed: 0.4070123094134033
Once a problematic seed is determined, it can be provided back to any so that
the generation becomes repeatable.
$ ANY_SEED=0.4070123094134033 mocha --recursive test/unit/