Preparation

1. Login into Admin Console
2. Go to User Management → Administrators section
3. Add administrator with username tester1, enter all required fields and save.
4. Add administrator with username tester2, enter all required fields and save.
5. Go to Configuration → Website → Advanced section
6. Set Left Menu (Tree) Width setting to 300 and save changes.

Testing (part 1)

1. Login into Admin Console as root user
2. Make left menu width 2 times wider by dragging its right border
3. Wait for 1 second (new width will be saved)
4. Reload page (whole frameset)
5. Confirm, that menu width is the same as before page reload
6. Logout

Testing (part 2)

1. Login into Admin Console as tester1 user
2. Confirm left menu width matches one, that was entered in Left Menu (Tree) Width system setting (the 300px)
3. Logout

Testing (part 3)

1. Login into admin console as tester2 user
2. Go to Configuration → Website → Advanced section
3. Remove value from Left Menu (Tree) Width setting and save changes.
4. Reload page (whole frameset)
5. Confirm, that menu width is now 200px