scroll visible snapshot (#2225)

* scroll visible snapshot

* change text of test

tests/snapshot_tests/snapshot_apps/scroll_visible.py

@@ -0,0 +1,23 @@
+from textual.app import App, ComposeResult
+from textual.containers import VerticalScroll
+from textual.widgets import Label, Static
+
+
+# Checks  https://github.com/Textualize/textual/issues/2181
+class MyCustomWidget(Static):
+    def compose(self) -> ComposeResult:
+        yield Label(("|\n" * 100)[:-1])
+        yield Label("SHOULD BE VISIBLE", id="target")
+
+
+class MyApp(App):
+    def compose(self) -> ComposeResult:
+        with VerticalScroll():
+            yield MyCustomWidget()
+
+    def key_t(self) -> None:
+        self.query_one("#target").scroll_visible()
+
+
+if __name__ == "__main__":
+    MyApp().run()