Try, for example, with https://www.drupal.org/project/entityreference_dragdrop, whose info.yml file says:
name: Entity Reference Drag & Drop
As for tests, I can see a theme whose name contains special characters, presumably for testing this (modules/block/tests/modules/block_test/themes/block_test_specialchars_theme/block_test_specialchars_theme.info.yml), but we don't seem to have a module for this! So that means there's maybe no test coverage for the Extend page, even though that gets the escaping right.