Support read/write of noise msg and payload

tests/security/noise/test_msg_read_writer.py

@@ -0,0 +1,27 @@
+import pytest
+
+from libp2p.security.noise.io import MAX_NOISE_MESSAGE_LEN, NoisePacketReadWriter
+from libp2p.tools.factories import raw_conn_factory
+
+
+@pytest.mark.parametrize(
+    "noise_msg",
+    (b"", b"data", pytest.param(b"A" * MAX_NOISE_MESSAGE_LEN, id="maximum length")),
+)
+@pytest.mark.trio
+async def test_noise_msg_read_write_round_trip(nursery, noise_msg):
+    async with raw_conn_factory(nursery) as conns:
+        reader, writer = (
+            NoisePacketReadWriter(conns[0]),
+            NoisePacketReadWriter(conns[1]),
+        )
+        await writer.write_msg(noise_msg)
+        assert (await reader.read_msg()) == noise_msg
+
+
+@pytest.mark.trio
+async def test_noise_msg_write_too_long(nursery):
+    async with raw_conn_factory(nursery) as conns:
+        writer = NoisePacketReadWriter(conns[0])
+        with pytest.raises(ValueError):
+            await writer.write_msg(b"1" * (MAX_NOISE_MESSAGE_LEN + 1))