Link to Boost Test Library

doc/contributing.rst

@@ -535,10 +535,11 @@ sporting a single monolithic :file:`test_sidechains.py`.
 
 |python| code is evaluated using its own
 :py_docs:`unit testing framework <library/unittest.html>` with a little help
-from |ost_s|_. The basic scheme is to import your module, subclass
-:class:`unittest.TestCase` and make the whole file runnable as script using the
-most common |nameattr|_ attribute. A file :file:`tests/test_something.py` could
-look like this, carrying a single test case:
+from |ost_s|_ (|C++| uses the |boost| `Test Library <http://www.boost.org/doc/libs/1_47_0/libs/test/doc/html/index.html>`_).
+The basic scheme is to import your module, subclass :class:`unittest.TestCase`
+and make the whole file runnable as script using the most common |nameattr|_
+attribute. A file :file:`tests/test_something.py` could look like this,
+carrying a single test case:
 
 .. testcode:: promod3unittest
   :hide: