There are a number of positive and negative API tests in manila-tempest-plugin:

https://github.com/openstack/manila-tempest-plugin/blob/master/manila_tempest_tests/tests/api/admin/test_share_manage.py

https://github.com/openstack/manila-tempest-plugin/blob/master/manila_tempest_tests/tests/api/admin/test_snapshot_manage.py

https://github.com/openstack/manila-tempest-plugin/blob/master/manila_tempest_tests/tests/api/admin/test_share_manage_negative.py 

https://github.com/openstack/manila-tempest-plugin/blob/master/manila_tempest_tests/tests/api/admin/test_snapshot_manage_negative.py 

We suspect these "API" are sufficient. These tests are currently disabled in the CephFS test jobs in the CI.

However, we identified atleast one "scenario" test that could use improvement:

https://github.com/openstack/manila-tempest-plugin/blob/master/manila_tempest_tests/tests/scenario/test_share_manage_unmanage.py

This test needs to support the CEPHFS protocol. 

Also, 

we need a scenario test that tests a managed snapshot in the same way. There was a test case specification that was spelled out here: https://specs.openstack.org/openstack/manila-specs/specs/release_independent/scenario-tests.html#create-manage-share-and-snapshot-and-write-data