Completely overhaul the documentation

readthedocs/developing/test-servers.rst

@@ -0,0 +1,37 @@
+============
+Test Servers
+============
+
+
+To run Telethon on a test server, use the following code:
+
+.. code-block:: python
+
+    client = TelegramClient(None, api_id, api_hash)
+    client.session.set_dc(dc_id, '149.154.167.40', 80)
+
+You can check your ``'test ip'`` on https://my.telegram.org.
+
+You should set ``None`` session so to ensure you're generating a new
+authorization key for it (it would fail if you used a session where you
+had previously connected to another data center).
+
+Note that port 443 might not work, so you can try with 80 instead.
+
+Once you're connected, you'll likely be asked to either sign in or sign up.
+Remember `anyone can access the phone you
+choose <https://core.telegram.org/api/datacenter#testing-redirects>`__,
+so don't store sensitive data here.
+
+Valid phone numbers are ``99966XYYYY``, where ``X`` is the ``dc_id`` and
+``YYYY`` is any number you want, for example, ``1234`` in ``dc_id = 2`` would
+be ``9996621234``. The code sent by Telegram will be ``dc_id`` repeated five
+times, in this case, ``22222`` so we can hardcode that:
+
+.. code-block:: python
+
+    client = TelegramClient(None, api_id, api_hash)
+    client.session.set_dc(2, '149.154.167.40', 80)
+    client.start(
+        phone='9996621234', code_callback=lambda: '22222'
+    )