This test requires a site in which you can uninstall plugins i.e. not the QA testing site.
- Log in as an admin and create a course in Weekly format.
- Go to 'Manage course formats' in the Site administration.
- Verify that the default course format is Topics and it is not possible to uninstall it.
- Uninstall the Weekly format.
- Go to the course previously created in Weekly format and verify that it is now in Topics format.