Remove debug print statements and unnecessary pause in App class; add…

… on_mount method to LazyApp for better lifecycle management in tests

src/textual/app.py

@@ -1955,7 +1955,6 @@ async def run_app(app: App[ReturnType]) -> None:
             try:
                 pilot = Pilot(app)
                 await pilot._wait_for_screen()
-                await pilot.pause()
                 yield pilot
             finally:
                 # Shutdown the app cleanly
@@ -3709,13 +3708,11 @@ async def on_event(self, event: events.Event) -> None:
             if isinstance(event, events.MouseEvent):
                 # Record current mouse position on App
                 self.mouse_position = Offset(event.x, event.y)
-                print("mouse event (on_event)", event)
                 if isinstance(event, events.MouseDown):
                     try:
                         self._mouse_down_widget, _ = self.get_widget_at(
                             event.x, event.y
                         )
-                        print("mouse down widget (on_event)", self._mouse_down_widget)
                     except NoWidget:
                         # Shouldn't occur, since at the very least this will find the Screen
                         self._mouse_down_widget = None
@@ -3728,12 +3725,10 @@ async def on_event(self, event: events.Event) -> None:
                     isinstance(event, events.MouseUp)
                     and self._mouse_down_widget is not None
                 ):
-                    print("mouse up (on_event)", event)
                     try:
                         screen_offset = event.screen_offset
                         mouse_down_widget = self._mouse_down_widget
                         mouse_up_widget, _ = self.get_widget_at(*screen_offset)
-                        print("mouse up widget (on_event)", mouse_up_widget)
                         if mouse_up_widget is mouse_down_widget:
                             same_offset = (
                                 self._click_chain_last_offset is not None
@@ -3753,7 +3748,6 @@ async def on_event(self, event: events.Event) -> None:
                             click_event = events.Click.from_event(
                                 mouse_down_widget, event, chain=self._chained_clicks
                             )
-                            print("generated click event (on_event)", click_event)
 
                             self._click_chain_last_time = event.time
                             self._click_chain_last_offset = screen_offset

tests/test_lazy.py

@@ -12,13 +12,20 @@ def compose(self) -> ComposeResult:
             with Horizontal():
                 yield Label(id="bar")
 
+    def on_mount(self) -> None:
+        print("on_mount")
+
 
 async def test_lazy():
     app = LazyApp()
     async with app.run_test() as pilot:
         # No #foo on initial mount
+        print("before query #foo")
         assert len(app.query("#foo")) == 0
+        print("after query #foo")
+        print("before query #bar")
         assert len(app.query("#bar")) == 1
+        print("after query #bar")
         await pilot.pause()
         await pilot.pause()
         # #bar mounted after refresh