added test

tests/test_connections.py

+# coding: utf-8
+
+import asyncio
+
+import pytest
+
+from asyncua import Client
+from asyncua.ua.uaerrors import BadMaxConnectionsReached
+
+from .conftest import port_num
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_max_connections_1(opc):
+    opc.server.iserver.isession.__class__.max_connections = 1
+    port = opc.server.endpoint.port
+    if port == port_num:
+        # if client we already have one connection
+        with pytest.raises(BadMaxConnectionsReached):
+            async with Client(f'opc.tcp://127.0.0.1:{port}'):
+                pass
+    else:
+        async with Client(f'opc.tcp://127.0.0.1:{port}'):
+            with pytest.raises(BadMaxConnectionsReached):
+                async with Client(f'opc.tcp://127.0.0.1:{port}'):
+                    pass
+    opc.server.iserver.isession.__class__.max_connections = 1000