Update test servers documentation (#700)

readthedocs/extra/developing/test-servers.rst

@@ -8,8 +8,7 @@ To run Telethon on a test server, use the following code:
     .. code-block:: python
 
         client = TelegramClient(None, api_id, api_hash)
-        client.session.server_address = '149.154.167.40'
-        client.connect()
+        client.session.set_dc(dc_id, '149.154.167.40', 80)
 
 You can check your ``'test ip'`` on https://my.telegram.org.
 
@@ -17,16 +16,20 @@ 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).
 
-Once you're connected, you'll likely need to ``.sign_up()``. Remember
-`anyone can access the phone you
+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:
+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
 
-        from random import randint
-
-        dc_id = '2'  # Change this to the DC id of the test server you chose
-        phone = '99966' + dc_id + str(randint(9999)).zfill(4)
-        client.send_code_request(phone)
-        client.sign_up(dc_id * 5, 'Some', 'Name')
+        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')