unit testing tcp connection to the broker

pyproject.toml

@@ -26,6 +26,7 @@ passlib = "^1.7.0"
 docopt = "^0.6.0"
 PyYAML = ">=5.4.0,<7.0"
 coveralls = {version = "^3.0.1", optional = true}
+psutil = "^5.9.0"
 
 
 [tool.poetry.extras]

tests/test_broker.py

@@ -4,6 +4,8 @@
 import asyncio
 import logging
 from unittest.mock import call, MagicMock
+import socket
+import psutil
 
 import pytest
 
@@ -93,6 +95,42 @@ async def test_client_connect(broker, mock_plugin_manager):
     )
 
 
+@pytest.mark.asyncio
+async def test_connect_tcp(broker):
+    process = psutil.Process()
+    connections_number = 10
+    sockets = [
+        socket.create_connection(("127.0.0.1", 1883)) for _ in range(connections_number)
+    ]
+    connections = process.connections()
+    await asyncio.sleep(0.1)
+
+    # max number of connections is 10
+    assert broker._servers["default"].conn_count == connections_number
+    # Extra connection for the listening Broker
+    assert len(connections) == connections_number + 1
+    for conn in connections:
+        assert conn.status == "ESTABLISHED" or conn.status == "LISTEN"
+
+    # close all connections
+    for s in sockets:
+        s.close()
+    connections = process.connections()
+    for conn in connections:
+        assert conn.status == "CLOSE_WAIT" or conn.status == "LISTEN"
+    await asyncio.sleep(0.1)
+    assert broker._servers["default"].conn_count == 0
+
+    # Add one more connection
+    s = socket.create_connection(("127.0.0.1", 1883))
+    open_connections = []
+    for conn in process.connections():
+        if conn.status == "ESTABLISHED":
+            open_connections.append(conn)
+    assert len(open_connections) == 1
+    assert broker._servers["default"].conn_count == 1
+
+
 @pytest.mark.asyncio
 async def test_client_connect_will_flag(broker):
     conn_reader, conn_writer = await asyncio.open_connection("127.0.0.1", 1883)