📝 (testing.md): add documentation for testing WebSocket actions and channels with TestClient

Author: SpaceShaman

docs/Usage/testing.md

@@ -0,0 +1,53 @@
+# Testing
+
+SocketAPI includes a built-in `TestClient` based on Starlette's test client, making it easy to test your WebSocket actions and channels.
+
+## Basic Usage
+
+```python
+from socketapi import SocketAPI
+from socketapi.testclient import TestClient
+
+app = SocketAPI()
+
+@app.action("calculate")
+async def calculate(a: int, b: int) -> int:
+    return a + b
+
+@app.channel("notifications")
+async def notifications(message: str):
+    return {"message": message}
+
+def test_action():
+    client = TestClient(app)
+    
+    with client.websocket_connect("/") as websocket:
+        # Send action request
+        websocket.send_json({
+            "type": "action",
+            "channel": "calculate",
+            "data": {"a": 5, "b": 3}
+        })
+        
+        # Receive response
+        response = websocket.receive_json()
+        assert response["data"] == 8
+        assert response["status"] == "completed"
+
+def test_channel():
+    client = TestClient(app)
+    
+    with client.websocket_connect("/") as websocket:
+        # Subscribe to channel
+        websocket.send_json({
+            "type": "subscribe",
+            "channel": "notifications"
+        })
+        
+        # Receive subscription confirmation
+        response = websocket.receive_json()
+        assert response["type"] == "subscribed"
+        assert response["channel"] == "notifications"
+```
+
+The `TestClient` provides a simple way to test your WebSocket endpoints without running a live server.