Enable resetting factory.fuzzy's random generator (Closes #175, #185).

Users may now call ``factory.fuzzy.get_random_state()`` to retrieve
the current random generator's state (isolated from the one used in
Python's ``random``).

That state can then be reinjected with
``factory.fuzzy.set_random_state(state)``.

2 files changed, 34 insertions, 0 deletions

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 018ec60..ebe9930 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -7,6 +7,10 @@ ChangeLog
 2.5.0 (master)
 --------------
 
+*New:*
+
+    - Add support for getting/setting :mod:`factory.fuzzy`'s random state (see :issue:`175`, :issue:`185`).
+
 *Deprecation:*
 
     - Remove deprecated features from :ref:`v2.4.0`
diff --git a/docs/fuzzy.rst b/docs/fuzzy.rst
index 1480419..0658652 100644
--- a/docs/fuzzy.rst
+++ b/docs/fuzzy.rst
@@ -338,3 +338,33 @@ They should inherit from the :class:`BaseFuzzyAttribute` class, and override its
 
         The method responsible for generating random values.
         *Must* be overridden in subclasses.
+
+
+Managing randomness
+-------------------
+
+Using :mod:`random` in factories allows to "fuzz" a program efficiently.
+However, it's sometimes required to *reproduce* a failing test.
+
+:mod:`factory.fuzzy` uses a separate instance of :class:`random.Random`,
+and provides a few helpers for this:
+
+.. method:: get_random_state()
+
+    Call :meth:`get_random_state` to retrieve the random generator's current
+    state.
+
+.. method:: set_random_state(state)
+
+    Use :meth:`set_random_state` to set a custom state into the random generator
+    (fetched from :meth:`get_random_state` in a previous run, for instance)
+
+.. method:: reseed_random(seed)
+
+    The :meth:`reseed_random` function allows to load a chosen seed into the random generator.
+
+
+Custom :class:`BaseFuzzyAttribute` subclasses **SHOULD**
+use :obj:`factory.fuzzy._random` foras a randomness source; this ensures that
+data they generate can be regenerated using the simple state from
+:meth:`get_random_state`.