do not clear all decorated pages during AppHarness tests (#3093)

reflex/testing.py

@@ -124,6 +124,7 @@ class AppHarness:
     backend: Optional[uvicorn.Server] = None
     state_manager: Optional[StateManagerMemory | StateManagerRedis] = None
     _frontends: list["WebDriver"] = dataclasses.field(default_factory=list)
+    _decorated_pages: list = dataclasses.field(default_factory=list)
 
     @classmethod
     def create(
@@ -230,11 +231,15 @@ class AppHarness:
         with chdir(self.app_path):
             # ensure config and app are reloaded when testing different app
             reflex.config.get_config(reload=True)
-            # Clean out any `rx.page` decorators from other tests.
-            reflex.app.DECORATED_PAGES.clear()
+            # Save decorated pages before importing the test app module
+            before_decorated_pages = reflex.app.DECORATED_PAGES.copy()
             # Ensure the AppHarness test does not skip State assignment due to running via pytest
             os.environ.pop(reflex.constants.PYTEST_CURRENT_TEST, None)
             self.app_module = reflex.utils.prerequisites.get_compiled_app(reload=True)
+            # Save the pages that were added during testing
+            self._decorated_pages = [
+                p for p in reflex.app.DECORATED_PAGES if p not in before_decorated_pages
+            ]
         self.app_instance = self.app_module.app
         if isinstance(self.app_instance._state_manager, StateManagerRedis):
             # Create our own redis connection for testing.
@@ -396,6 +401,10 @@ class AppHarness:
         for driver in self._frontends:
             driver.quit()
 
+        # Cleanup decorated pages added during testing
+        for page in self._decorated_pages:
+            reflex.app.DECORATED_PAGES.remove(page)
+
     def __exit__(self, *excinfo) -> None:
         """Contextmanager protocol for `stop()`.