default_seed is used initialize the pseudo-random generator that chooses random
values from generators, in each test that is not provided its own seed.
default_trial_count determines the number of trials per test, except in tests
that explicitly override it.
default_trial_count_for_test_no_duplicates determines the number of trials when
running test_no_duplicates without ~trials, either as a constant or as a factor
of default_trial_count.
default_attempts_per_trial determines the maximum number of attempts to generate
inputs for trials, as a multiplier for the number of trials, except in tests that
explicitly override it.
default_probability_threshold_to_remember_choice determines the minimum
probability, out of 1.0, at which Quickcheck.iter and derived functions will
remember previous choices and avoid repeating them. Below this threshold, it is
assumed that the space needed to record the choice outweighs the negligible chance
of repeating it.
default_shrink_attempts determines the number of attempts at shrinking
when running test or iter with ~shrinker and without
~shrink_attempts