This test requires a site in which you can uninstall plugins i.e. not the QA testing site.

1. Log in as an admin and create a course in Weekly format.
2. Go to 'Manage course formats' in the Site administration.
3. Verify that the default course format is Topics and it is not possible to uninstall it.
4. Uninstall the Weekly format.
5. Go to the course previously created in Weekly format and verify that it is now in Topics format.