Add a doc describing how to write e2e tests

doc/contributing.rst

@@ -50,35 +50,13 @@ Tests
 There are two test suites for biboumi:
 
 - unit tests that can be run simply using `make check`.
-  These tests use the Catch test framework, are written in pure C++
+  These tests use the Catch2 test framework, are written in pure C++
   and they should always succeed, in all possible build configuration.
 
 - a more complex end-to-end test suite. This test suite is written in python3,
   uses a specific IRC server (`charybdis`_), and only tests the most complete
-  biboumi configuration (when all dependencies are used). To run it, you need
-  to install various dependencies: refer to fedora’s `Dockerfile.base`_ and
-  `Dockerfile`_ to see how to install charybdis, slixmpp, botan, a ssl
-  certificate, etc.
-
-  Once all the dependencies are correctly installed, the tests are run with
-
-.. code-block:: sh
-
-  make e2e
-
-To run one or more specific tests, you can do something like this:
-
-.. code-block:: sh
-
-  make biboumi && python3 ../tests/end_to_end  self_ping  basic_handshake_success
-
-This will run two tests, self_ping and basic_handshake_success.
-
-To write additional tests, you need to add a Scenario
-into `the __main__.py file`_. If you have problem running this end-to-end
-test suite, or if you struggle with this weird code (that would be
-completely normal…), don’t hesitate to ask for help.
-
+  biboumi configuration (when all dependencies are used).
+  Read more about these tests in the specific documentation TODO.
 
 All these tests automatically run with various configurations, on various
 platforms, using gitlab CI.