🐛 Ensure rich_markup_mode=None disables Rich formatting

tests/test_rich_markup_mode.py

@@ -0,0 +1,40 @@
+import typer
+import typer.completion
+from typer.testing import CliRunner
+
+runner = CliRunner()
+rounded = ["╭", "─", "┬", "╮", "│", "├", "┼", "┤", "╰", "┴", "╯"]
+
+
+def test_rich_markup_mode_none():
+    app = typer.Typer(rich_markup_mode=None)
+
+    @app.command()
+    def main(arg: str):
+        """Main function"""
+        print(f"Hello {arg}")
+
+    assert app.rich_markup_mode is None
+
+    result = runner.invoke(app, ["World"])
+    assert "Hello World" in result.stdout
+
+    result = runner.invoke(app, ["--help"])
+    assert all(c not in result.stdout for c in rounded)
+
+
+def test_rich_markup_mode_rich():
+    app = typer.Typer(rich_markup_mode="rich")
+
+    @app.command()
+    def main(arg: str):
+        """Main function"""
+        print(f"Hello {arg}")
+
+    assert app.rich_markup_mode == "rich"
+
+    result = runner.invoke(app, ["World"])
+    assert "Hello World" in result.stdout
+
+    result = runner.invoke(app, ["--help"])
+    assert any(c in result.stdout for c in rounded)