This test requires a test user with default user picture and an email address which has a gravatar associated to it.
1. Login as an administrator and enable gravatars in Settings > Site administration > Users > Permissions > User policies.
2. View the profile of the test user and check that the default user picture has been replaced with the gravatar.
3. Login as the test user, edit your profile and upload a new user picture.
4. Save changes and check that the gravatar has been replaced with the uploaded picture (may require a page refresh).