Add test confirming one WebSocket per page

- Add  Playwright test that navigates
  to the base page and asserts only one unique WebSocket URL is used
  across all component mounts.
- Update changelog with brief entry under Changed.

Author: User

CHANGELOG.md

@@ -25,6 +25,7 @@ Don't forget to remove deprecated code on each major release!
 
 ### Changed
 
+- Use one WebSocket per client webpage.
 - Updated dependencies: `reactpy>=2.0.0, <3.0.0` and `reactpy-router>=3.0.0, <4.0.0`.
 - Updated Python support to 3.11–3.14.
 - Replaced PyScript `<py-script>` tags with standard `<script type="py">` tags.

tests/test_app/tests/test_components.py

@@ -21,6 +21,26 @@ class ComponentTests(PlaywrightTestCase):
     # Generic Component Tests #
     ###########################
 
+    def test_one_websocket_per_page(self):
+        """Confirm that all components on a page share a single WebSocket."""
+        websocket_urls: list[str] = []
+
+        def track_ws(ws):
+            websocket_urls.append(ws.url)
+
+        self.page.on("websocket", track_ws)
+        try:
+            self.page.goto(f"http://{self.host}:{self._port_0}/")
+            self.page.wait_for_selector("#hello-world")
+            self.page.wait_for_selector("#button")
+            self.page.wait_for_selector("#parametarized-component")
+            unique_urls = set(websocket_urls)
+            assert len(unique_urls) == 1, (
+                f"Expected 1 unique WebSocket URL, got {len(unique_urls)}: {unique_urls}"
+            )
+        finally:
+            self.page.remove_listener("websocket", track_ws)
+
     @navigate_to_page("/")
     def test_component_hello_world(self):
         self.page.wait_for_selector("#hello-world")