test(cli): exercise standalone sign-in with and without a built page

Use the real aiohttp Application while replacing the runner and TCP site,
so build_app can register its response hook without a partial fake.

Resolve the UI from temporary candidates, cover both page states, and
assert that revalidation is registered only when a built page is served.
Correct the startup comment now that the coroutine is exercised in tests.

Author: LivXue

raven/cli/serve_commands.py

@@ -411,9 +411,8 @@ async def _serve_main(port: int, open_browser: bool) -> None:
     from raven.rpc.transports.ws import WsGateway, build_app, pick_port
 
     register_console_feature()
-    # This coroutine binds a port and serves until it is killed, so no test
-    # runs it; what it schedules is pinned by source in
-    # tests/test_cli_serve_commands.py instead.
+    # Startup tests replace this background warm-up to keep provider
+    # initialization out of the serving probe.
     warm_up_in_background()  # pragma: no cover
 
     # Declared before anything can emit a span. The page runs on the terminal's

tests/test_cli_serve_commands.py

@@ -470,24 +470,8 @@ async def _teardown() -> None:
             build_error=None, agent_loop=None, deliverables=None, dispatcher=None, teardown=_teardown
         )
 
-    class _Application:
-        """The three things `build_app` touches on a real aiohttp application."""
-
-        def __init__(self) -> None:
-            self.router = self
-            self.on_shutdown: list = []
-
-        def add_get(self, *_args, **_kwargs) -> None:
-            pass
-
-        def add_post(self, *_args, **_kwargs) -> None:
-            pass
-
-        def add_static(self, *_args, **_kwargs) -> None:
-            pass
-
     class _Runner:
-        """`AppRunner`/`TCPSite`: the four awaitables `_serve_main` uses."""
+        """`AppRunner`/`TCPSite` without binding sockets."""
 
         def __init__(self, *_args) -> None:
             pass
@@ -532,14 +516,21 @@ def test_a_standalone_serve_opens_through_the_same_path(self) -> None:
         assert "_open(auth_url)" in src
         assert "webbrowser.open" not in src
 
-    async def test_a_standalone_serve_prints_the_link_it_opens(self, monkeypatch, opened: list[str]) -> None:
+    @pytest.mark.parametrize("built_page", [False, True], ids=["without-page", "with-page"])
+    async def test_a_standalone_serve_prints_the_link_it_opens(
+        self, two_candidates, built_page: bool, monkeypatch, opened: list[str]
+    ) -> None:
         """The standalone path, run rather than read: the URL it hands the browser
         is one the gateway minted, and the launch that asked for a browser is the
-        one that gets one."""
+        one that gets one, with or without a built page."""
         from contextlib import suppress
 
         from raven.cli import serve_commands as sc
 
+        packaged, _source = two_candidates
+        if built_page:
+            _build(packaged, "page")
+
         printed: list[str] = []
         monkeypatch.setattr(sc.typer, "echo", printed.append)
 
@@ -563,9 +554,14 @@ async def _nothing() -> None:
 
         from aiohttp import web
 
-        monkeypatch.setattr(web, "AppRunner", TestTheSignInLink._Runner)
+        apps: list[web.Application] = []
+
+        def _runner(app: web.Application) -> TestTheSignInLink._Runner:
+            apps.append(app)
+            return self._Runner()
+
+        monkeypatch.setattr(web, "AppRunner", _runner)
         monkeypatch.setattr(web, "TCPSite", TestTheSignInLink._Runner)
-        monkeypatch.setattr(web, "Application", TestTheSignInLink._Application)
         monkeypatch.setattr(serve_commands, "_announce_updates", lambda *a, **k: _nothing())
         monkeypatch.setattr(serve_commands, "_write_serve_state", lambda *a, **k: None)
 
@@ -575,6 +571,9 @@ async def _nothing() -> None:
         assert len(opened) == 1
         assert opened[0].startswith("http://127.0.0.1:18999/auth#")
         assert f"sign in with this link (it works once): {opened[0]}" in printed
+        (app,) = apps
+        assert isinstance(app, web.Application)
+        assert any(hook.__name__ == "revalidate" for hook in app.on_response_prepare) is built_page
 
 
 class _FakeProc: