Test client doesn't encode/decode the data

[senstar-nross]

Sending data with emit() and getting the data back with get_received() returns the actual object emitted not one that got encoded to json and back. This can mask at least 2 different types of bugs.

The real socketio client encodes the data in packet.py encode()

    if data is not None:
        if needs_comma:
            encoded_packet += ','
        encoded_packet += self.json.dumps(data, separators=(',', ':'))

but the socketio test client just stores the object for later retrieval.

This caused my test code to miss two errors:

1. The object I sent was not json encodable and caused an exception.
2. If you change the object after emit the changes appear when you get the data from get_received(). I had a test that passed because the object that was emitted had wrong data that was emitted but was changed to correct data later. This passed in test but failed in production

Steps to reproduce the behavior:
Case 1:

1. in a flask app emit an object with an non-json encodable type (like datetime or mongo ObjectId)
2. test with pytest using socketio.test_client
3. code will run
4. test again without using pytest code will throw an exception (TypeError: Object of type ObjectId is not JSON serializable)

Case 2:
#in server
data = {'test': 1}
emit('test', data)
data['test']=2

#in pytest
assert socketio_client.get_received()[0]['args'][0]['test'] == 1 #this assert will fail

Expected behavior
In the first case should throw an exception
in the second case the assertion should pass

[senstar-nross]

what about just calling pkt.decode(pkt.encode()) in test_client.py?

def __init__(self, app, socketio, namespace=None, query_string=None,
             headers=None, flask_test_client=None):
    def _mock_send_packet(sid, pkt):
        pkt.decode(pkt.encode())  #<<<<<<<<<<<<<<<<<<<<<<
        if pkt.packet_type == packet.EVENT or \
                pkt.packet_type == packet.BINARY_EVENT:
 ...

[senstar-nross]

well that didn't work :(

[senstar-nross]

I have no idea if i should submit a PR for this or not. I haven't ever contributed to a project before. so anyway, i think this works. It forces the encoding for non binary events and fixes the two issue that i noted above...