test: enhance multi-tab coverage for concurrency and events

backend/test_browser_tabs.py

@@ -145,3 +145,46 @@ async def test_ensure_open_discards_session_if_all_tabs_closed(service, session)
         await service.screenshot(session.id)
     
     assert session.id not in service._sessions
+
+@pytest.mark.asyncio
+async def test_tab_revision_bumps_on_events(service, session):
+    # Setup listeners for the initial tab
+    service._setup_tab_listeners(session, session.tabs["tab1"].page)
+    
+    # Extract the "load" listener callback
+    calls = session.tabs["tab1"].page.on.call_args_list
+    load_callback = next(c[0][1] for c in calls if c[0][0] == "load")
+    
+    initial_revision = session.tab_revision
+    load_callback()
+    assert session.tab_revision == initial_revision + 1
+
+@pytest.mark.asyncio
+async def test_session_state_concurrency_with_popup(service, session):
+    # Setup: page.title() will trigger a new page registration in background
+    triggered = False
+    async def mock_title():
+        nonlocal triggered
+        # Only trigger popup once (state() calls title twice: once for tabs list, once for top-level)
+        if not triggered:
+            triggered = True
+            # Simulate a popup arriving while title is being fetched
+            new_page = AsyncMock()
+            new_page.on = MagicMock()
+            new_page.is_closed = MagicMock(return_value=False)
+            service._handle_new_page(session, new_page)
+        # Yield to let the registration task start (it will block on the lock)
+        await asyncio.sleep(0.01)
+        return "Initial Tab"
+    
+    session.tabs["tab1"].page.title = mock_title
+    
+    # Call state() which takes the lock and calls _session_state (which calls mock_title)
+    state = await service.state(session.id)
+    
+    assert len(state["tabs"]) == 1 # Still 1 because popup registration is waiting for lock
+    
+    # Yield to let registration task finish after state() released the lock
+    await asyncio.sleep(0.1)
+    assert len(session.tabs) == 2
+    assert session.tab_revision > 0