This test requires a course set up in Topics format but with the default course format as Weeks (identified in Settings>Site administration>Courses>Course default settings)

Test steps:
1.As admin, navigate to Settings>Site administration>Plugins>Course formats>Manage course formats.
2.Verify that you can't delete Weekly format as it is the default format.
3.Disable Single activity and Social format
4. Log in as a teacher to your Topics format course and verify that in Course administration>Edit settings>Format you can only change to Weekly format.
5. As admin, re-enable Single activity and Social format and disable Topics format.
6. As a teacher return to your course. Verify that it is still in Topics format but that when you access Course administration>Edit settings>Format you see the note "Topics format(disabled)"
7. As admin, navigate back to the Manage course formats screen. Click the link "Course default settings" and verify that you can't change the default to Topics (since it is disabled)
8. Now re-enable Topics format and verify that in "Course default settings" you now can change the default to Topics.Change it
9. Verify that Topics format is now default and can't be deleted.
10. As a teacher, return to your course. Verify that in Course administration>Edit settings>Format you see all four options.