Add note on check_accept to testing documentation (#676)

When writing tests, sometimes consumers are expected to reject connections, and while there is a check_accept parameter on send_and_consume, it's not documented. This commit adds a note on the use of the parameter to the docs.

docs/testing.rst

@@ -127,6 +127,7 @@ purpose use ``send_and_consume`` method::
             client.send_and_consume('my_internal_channel', {'value': 'my_value'})
             self.assertEqual(client.receive(), {'all is': 'done'})
             
+*Note: if testing consumers that are expected to close the connection when consuming, set the ``check_accept`` parameter to False on ``send_and_consume``.*
 
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