add tests

Author: Archmonger

tests/test_app/offline/components.py

@@ -4,11 +4,12 @@
 @component
 def online():
     return html.div(
+        {"id": "online"},
         "This is the ONLINE component. "
-        "Try shutting down your webserver and checking if the offline component appears."
+        "Shut down your webserver and check if the offline component appears.",
     )
 
 
 @component
 def offline():
-    return html.div({"id": "offline-success"}, "Offline")
+    return html.div({"id": "offline"}, "Offline")

tests/test_app/tests/test_components.py

@@ -46,12 +46,18 @@ def setUpClass(cls):
         cls._server_process.ready.wait()
         cls._port = cls._server_process.port.value
 
-        # Open the second server process
+        # Open the second server process, used for testing custom hosts
         cls._server_process2 = cls.ProtocolServerProcess(cls.host, get_application)
         cls._server_process2.start()
         cls._server_process2.ready.wait()
         cls._port2 = cls._server_process2.port.value
 
+        # Open the third server process, used for testing offline fallback
+        cls._server_process3 = cls.ProtocolServerProcess(cls.host, get_application)
+        cls._server_process3.start()
+        cls._server_process3.ready.wait()
+        cls._port3 = cls._server_process3.port.value
+
         # Open a Playwright browser window
         if sys.platform == "win32":
             asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())
@@ -67,9 +73,11 @@ def tearDownClass(cls):
         # Close the Playwright browser
         cls.playwright.stop()
 
-        # Close the second server process
+        # Close the other server processes
         cls._server_process2.terminate()
         cls._server_process2.join()
+        cls._server_process3.terminate()
+        cls._server_process3.join()
 
         # Repurposed from ChannelsLiveServerTestCase._post_teardown
         cls._server_process.terminate()
@@ -600,3 +608,20 @@ def test_url_router(self):
 
         finally:
             new_page.close()
+
+    def test_offline_components(self):
+        new_page = self.browser.new_page()
+        try:
+            server3_url = self.live_server_url.replace(
+                str(self._port), str(self._port3)
+            )
+            new_page.goto(f"{server3_url}/offline/")
+            new_page.wait_for_selector("div:not([hidden]) > #online")
+            self.assertIsNotNone(new_page.query_selector("div[hidden] > #offline"))
+            self._server_process3.terminate()
+            self._server_process3.join()
+            new_page.wait_for_selector("div:not([hidden]) > #offline")
+            self.assertIsNotNone(new_page.query_selector("div[hidden] > #online"))
+
+        finally:
+            new_page.close()