Add regression test for #2606.

tests/test_footer.py

@@ -0,0 +1,28 @@
+from textual.app import App, ComposeResult
+from textual.geometry import Offset
+from textual.screen import ModalScreen
+from textual.widgets import Footer, Label
+
+
+async def test_footer_highlight_when_pushing_modal():
+    """Regression test for https://github.com/Textualize/textual/issues/2606"""
+
+    class MyModalScreen(ModalScreen):
+        def compose(self) -> ComposeResult:
+            yield Label("apple")
+
+    class MyApp(App[None]):
+        BINDINGS = [("a", "p", "push")]
+
+        def compose(self) -> ComposeResult:
+            yield Footer()
+
+        def action_p(self):
+            self.push_screen(MyModalScreen())
+
+    app = MyApp()
+    async with app.run_test(size=(80, 2)) as pilot:
+        await pilot.hover(None, Offset(0, 1))
+        await pilot.click(None, Offset(0, 1))
+        assert isinstance(app.screen, MyModalScreen)
+        assert app.screen_stack[0].query_one(Footer).highlight_key is None