Improve OptionList test coverage (#2701)

* Cover the penultimate uncovered line in OptionList

Sort of moot, but worth a test that the control of a message is the option
list.

* Test OptionList hover over disabled option

I *would* have liked to have tested this sort of thing via snapshot tests,
but it seems that pilot.hover isn't quite behaving as desired there. But
this provides a useful test anyway.

tests/option_list/test_option_list_mouse_hover.py

@@ -13,7 +13,9 @@ class OptionListApp(App[None]):
 
     def compose(self) -> ComposeResult:
         yield Label("Something else to hover over")
-        yield OptionList(*[Option(str(n), id=str(n)) for n in range(10)])
+        yield OptionList(
+            *[Option(str(n), id=str(n), disabled=n == 3) for n in range(10)]
+        )
 
 
 async def test_no_hover() -> None:
@@ -41,6 +43,18 @@ async def test_hover_no_highlight() -> None:
         assert option_list._mouse_hovering_over != option_list.highlighted
 
 
+async def test_hover_disabled() -> None:
+    """The mouse hover value should react to the mouse hover over a disabled option."""
+    async with OptionListApp().run_test() as pilot:
+        await pilot.hover(OptionList, Offset(1, 3))
+        option_list = pilot.app.query_one(OptionList)
+        assert option_list._mouse_hovering_over == 3
+        assert option_list.get_option_at_index(
+            option_list._mouse_hovering_over
+        ).disabled
+        assert option_list._mouse_hovering_over != option_list.highlighted
+
+
 async def test_hover_then_leave() -> None:
     """After a mouse has been over an OptionList and left _mouse_hovering_over should be None again."""
     async with OptionListApp().run_test() as pilot:

tests/option_list/test_option_messages.py

@@ -20,6 +20,7 @@ class OptionListApp(App[None]):
 
     def _record(self, event: OptionList.OptionMessage) -> None:
         assert isinstance(event.option_id, str)
+        assert event.option_list is event.control
         self.messages.append(
             (event.__class__.__name__, event.option_id, event.option_index)
         )