Updated doc to include new feature that fixes #37

Author: pylessard

doc/source/udsoncan/client.rst

@@ -220,7 +220,7 @@ Suppress positive response
 The UDS standard proposes a mechanism to avoid treating useless positive responses. For all services using a subfunction byte, the client can set bit 7 of the subfunction byte to signal that no response is necessary if the response is positive. 
 This bit is called the ``suppressPosRspMsgIndicationBit``
 
-The ``Client`` object lets you use that feature by using ``suppress_positive_response`` into a ``with`` statement. See following example:
+The ``Client`` object lets you use that feature by using ``suppress_positive_response`` into a ``with`` statement. See the following example:
 
 .. code-block:: python
 
@@ -233,6 +233,35 @@ If ``suppress_positive_response`` is asking for a service with no subfunction by
 
 -----
 
+Overriding the output
+---------------------
+
+For mean of testing, it may be useful to send invalid payloads to the server and still want the ``Client`` object to parse the response of the server. 
+
+It is possible to do so by using the ``payload_override`` property into a ``with`` statement. See the following example:
+
+.. code-block:: python
+
+   with client.payload_override(b'\x11\x22\x33'): # Client will send 112233 (hex) in every call within this "with" statement
+      client.tester_present()
+
+It is also possible to override with a function that modify the original output
+
+.. code-block:: python
+   
+   def my_func(payload):
+      return payload + b'\x00'  # Add extra 00 to the payload
+
+   with client.payload_override(my_func): # Client will append 00 to its output
+      client.tester_present()
+
+When using that feature, the client will process the response from the server just like if a valid request was sent. The response may be :ref:`Invalid<InvalidResponseException>`, :ref:`Unexpected<UnexpectedResponseException>` or :ref:`Negative<NegativeResponseException>`.
+
+
+.. note:: It is possible to change the behaviour of the client on failing requests. See the client parameters :ref:`exception_on_invalid_response<config_exception_on_invalid_response>`, :ref:`exception_on_unexpected_response<config_exception_on_unexpected_response>` and :ref:`exception_on_negative_response<config_exception_on_negative_response>`
+
+-----
+
 Methods by services
 -------------------