Try the command ./run_tests.sh openstack_dashboards.dashboards.admin.flavors.test (This is if you want to run the test cases for flavors. Mention the path accordingly)

You can use this command: ./run_tests.sh openstack_dashboard.dashboards.admin.domains.tests

Where openstack_dashboard.dashboards.admin.domains.tests is the path to the test module.

Here is more details from the docs: https://github.com/openstack/horizon/blob/master/doc/source/ref/run_tests.rst#running-a-subset-of-tests (https://github.com/openstack/horizon/...)