Add extra snapshit tests

This tests the three main ways of making an option list, and ensures they
all turn out the same.

tests/snapshot_tests/snapshot_apps/option_list.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+from rich.text import Text
+
+from textual.app import App, ComposeResult
+from textual.containers import Horizontal
+from textual.widgets import OptionList
+from textual.widgets.option_list import Option
+
+
+class OptionListApp(App[None]):
+
+    def compose( self ) -> ComposeResult:
+        with Horizontal():
+            yield OptionList(
+                "One",
+                Option("Two"),
+                None,
+                Text.from_markup("[red]Three[/]")
+            )
+            yield OptionList(id="later-individual")
+            yield OptionList(id="later-at-once")
+
+    def on_mount(self) -> None:
+        options: list[None | str | Text | Option] = [
+            "One",
+            Option("Two"),
+            None,
+            Text.from_markup("[red]Three[/]"),
+        ]
+        option_list = self.query_one("#later-individual", OptionList)
+        for option in options:
+            option_list.add_option(option)
+        option_list.highlighted = 0
+        option_list = self.query_one("#later-at-once", OptionList)
+        option_list.add_options([
+            "One",
+            Option("Two"),
+            None,
+            Text.from_markup("[red]Three[/]"),
+        ])
+        option_list.highlighted = 0
+
+if __name__ == "__main__":
+    OptionListApp().run()

tests/snapshot_tests/test_snapshots.py

@@ -203,6 +203,8 @@ def test_option_list(snap_compare):
     assert snap_compare(WIDGET_EXAMPLES_DIR / "option_list_options.py")
     assert snap_compare(WIDGET_EXAMPLES_DIR / "option_list_tables.py")
 
+def test_option_list_build(snap_compare):
+    assert snap_compare(SNAPSHOT_APPS_DIR / "option_list.py")
 
 def test_progress_bar_indeterminate(snap_compare):
     assert snap_compare(WIDGET_EXAMPLES_DIR / "progress_bar_isolated_.py", press=["f"])