diff --git a/tempest/api/compute/admin/test_flavors_negative.py b/tempest/api/compute/admin/test_flavors_negative.py
index 34d8e3f..d1060c5 100644
--- a/tempest/api/compute/admin/test_flavors_negative.py
+++ b/tempest/api/compute/admin/test_flavors_negative.py
@@ -106,6 +106,5 @@
 @test.SimpleNegativeAutoTest
 class FlavorCreateNegativeTestJSON(base.BaseV2ComputeAdminTest,
                                    test.NegativeAutoTest):
-    _interface = 'json'
     _service = CONF.compute.catalog_type
     _schema = flavors.flavor_create
diff --git a/tempest/api/compute/base.py b/tempest/api/compute/base.py
index 4ad6c1d..808f78c 100644
--- a/tempest/api/compute/base.py
+++ b/tempest/api/compute/base.py
@@ -329,20 +329,17 @@
 
 class BaseV2ComputeTest(BaseComputeTest):
     _api_version = 2
-    _interface = "json"
 
 
 class BaseComputeAdminTest(BaseComputeTest):
     """Base test case class for Compute Admin API tests."""
-    _interface = "json"
 
     @classmethod
     def resource_setup(cls):
         super(BaseComputeAdminTest, cls).resource_setup()
         try:
             creds = cls.isolated_creds.get_admin_creds()
-            cls.os_adm = clients.Manager(
-                credentials=creds, interface=cls._interface)
+            cls.os_adm = clients.Manager(credentials=creds)
         except NotImplementedError:
             msg = ("Missing Compute Admin API credentials in configuration.")
             raise cls.skipException(msg)
diff --git a/tempest/api/compute/images/test_list_image_filters.py b/tempest/api/compute/images/test_list_image_filters.py
index 742c2dd..3f37a16 100644
--- a/tempest/api/compute/images/test_list_image_filters.py
+++ b/tempest/api/compute/images/test_list_image_filters.py
@@ -172,8 +172,6 @@
         # Verify only the expected number of results are returned
         params = {'limit': '1'}
         images = self.client.list_images(params)
-        # when _interface='xml', one element for images_links in images
-        # ref: Question #224349
         self.assertEqual(1, len([x for x in images if 'id' in x]))
 
     @test.attr(type='gate')
diff --git a/tempest/api/compute/servers/test_list_servers_negative.py b/tempest/api/compute/servers/test_list_servers_negative.py
index fd66d2b..4655f7f 100644
--- a/tempest/api/compute/servers/test_list_servers_negative.py
+++ b/tempest/api/compute/servers/test_list_servers_negative.py
@@ -101,7 +101,6 @@
         # List servers by specifying limits
         resp, body = self.client.list_servers({'limit': 1})
         self.assertEqual('200', resp['status'])
-        # when _interface='xml', one element for servers_links in servers
         self.assertEqual(1, len([x for x in body['servers'] if 'id' in x]))
 
     @test.attr(type=['negative', 'gate'])
diff --git a/tempest/api/compute/volumes/test_volumes_get.py b/tempest/api/compute/volumes/test_volumes_get.py
index 53f5ac0..69998d2 100644
--- a/tempest/api/compute/volumes/test_volumes_get.py
+++ b/tempest/api/compute/volumes/test_volumes_get.py
@@ -38,7 +38,7 @@
     def test_volume_create_get_delete(self):
         # CREATE, GET, DELETE Volume
         volume = None
-        v_name = data_utils.rand_name('Volume-%s-') % self._interface
+        v_name = data_utils.rand_name('Volume')
         metadata = {'Type': 'work'}
         # Create volume
         volume = self.client.create_volume(size=1,
diff --git a/tempest/api/compute/volumes/test_volumes_list.py b/tempest/api/compute/volumes/test_volumes_list.py
index c0ac99b..ba7ee6b 100644
--- a/tempest/api/compute/volumes/test_volumes_list.py
+++ b/tempest/api/compute/volumes/test_volumes_list.py
@@ -42,7 +42,7 @@
         cls.volume_list = []
         cls.volume_id_list = []
         for i in range(3):
-            v_name = data_utils.rand_name('volume-%s' % cls._interface)
+            v_name = data_utils.rand_name('volume')
             metadata = {'Type': 'work'}
             try:
                 volume = cls.client.create_volume(size=1,
diff --git a/tempest/api/data_processing/base.py b/tempest/api/data_processing/base.py
index 4c53a57..6c376fb 100644
--- a/tempest/api/data_processing/base.py
+++ b/tempest/api/data_processing/base.py
@@ -22,7 +22,6 @@
 
 
 class BaseDataProcessingTest(tempest.test.BaseTestCase):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/database/base.py b/tempest/api/database/base.py
index dd4c684..4f085b7 100644
--- a/tempest/api/database/base.py
+++ b/tempest/api/database/base.py
@@ -24,8 +24,6 @@
 class BaseDatabaseTest(tempest.test.BaseTestCase):
     """Base test case class for all Database API tests."""
 
-    _interface = 'json'
-
     @classmethod
     def resource_setup(cls):
         super(BaseDatabaseTest, cls).resource_setup()
diff --git a/tempest/api/database/limits/test_limits.py b/tempest/api/database/limits/test_limits.py
index 30d0a77..68a3884 100644
--- a/tempest/api/database/limits/test_limits.py
+++ b/tempest/api/database/limits/test_limits.py
@@ -18,7 +18,6 @@
 
 
 class DatabaseLimitsTest(base.BaseDatabaseTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/database/versions/test_versions.py b/tempest/api/database/versions/test_versions.py
index 80fcecf..3a32d0f 100644
--- a/tempest/api/database/versions/test_versions.py
+++ b/tempest/api/database/versions/test_versions.py
@@ -18,7 +18,6 @@
 
 
 class DatabaseVersionsTest(base.BaseDatabaseTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/test_roles.py b/tempest/api/identity/admin/test_roles.py
index c6c7dc3..80ad6db 100644
--- a/tempest/api/identity/admin/test_roles.py
+++ b/tempest/api/identity/admin/test_roles.py
@@ -21,7 +21,6 @@
 
 
 class RolesTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/test_roles_negative.py b/tempest/api/identity/admin/test_roles_negative.py
index 789e8b6..2c51715 100644
--- a/tempest/api/identity/admin/test_roles_negative.py
+++ b/tempest/api/identity/admin/test_roles_negative.py
@@ -23,7 +23,6 @@
 
 
 class RolesNegativeTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     def _get_role_params(self):
         self.data.setup_test_user()
diff --git a/tempest/api/identity/admin/test_services.py b/tempest/api/identity/admin/test_services.py
index 30e0058..af38afc 100644
--- a/tempest/api/identity/admin/test_services.py
+++ b/tempest/api/identity/admin/test_services.py
@@ -22,7 +22,6 @@
 
 
 class ServicesTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     def _del_service(self, service_id):
         # Deleting the service created in this method
diff --git a/tempest/api/identity/admin/test_tenant_negative.py b/tempest/api/identity/admin/test_tenant_negative.py
index a4bf263..16ea96a 100644
--- a/tempest/api/identity/admin/test_tenant_negative.py
+++ b/tempest/api/identity/admin/test_tenant_negative.py
@@ -23,7 +23,6 @@
 
 
 class TenantsNegativeTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     @test.attr(type=['negative', 'gate'])
     def test_list_tenants_by_unauthorized_user(self):
diff --git a/tempest/api/identity/admin/test_tenants.py b/tempest/api/identity/admin/test_tenants.py
index 549e952..cfae3a1 100644
--- a/tempest/api/identity/admin/test_tenants.py
+++ b/tempest/api/identity/admin/test_tenants.py
@@ -21,7 +21,6 @@
 
 
 class TenantsTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     @test.attr(type='gate')
     def test_tenant_list_delete(self):
diff --git a/tempest/api/identity/admin/test_tokens.py b/tempest/api/identity/admin/test_tokens.py
index bec621c..5323fde 100644
--- a/tempest/api/identity/admin/test_tokens.py
+++ b/tempest/api/identity/admin/test_tokens.py
@@ -19,7 +19,6 @@
 
 
 class TokensTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     @test.attr(type='gate')
     def test_create_get_delete_token(self):
diff --git a/tempest/api/identity/admin/test_users.py b/tempest/api/identity/admin/test_users.py
index 25312e8..9159468 100644
--- a/tempest/api/identity/admin/test_users.py
+++ b/tempest/api/identity/admin/test_users.py
@@ -21,7 +21,6 @@
 
 
 class UsersTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/test_users_negative.py b/tempest/api/identity/admin/test_users_negative.py
index 33a2f35..db8c564 100644
--- a/tempest/api/identity/admin/test_users_negative.py
+++ b/tempest/api/identity/admin/test_users_negative.py
@@ -23,7 +23,6 @@
 
 
 class UsersNegativeTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_credentials.py b/tempest/api/identity/admin/v3/test_credentials.py
index 6f2f6d4..f22ceec 100644
--- a/tempest/api/identity/admin/v3/test_credentials.py
+++ b/tempest/api/identity/admin/v3/test_credentials.py
@@ -19,7 +19,6 @@
 
 
 class CredentialsTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_default_project_id.py b/tempest/api/identity/admin/v3/test_default_project_id.py
index bd29cb8..72d323a 100644
--- a/tempest/api/identity/admin/v3/test_default_project_id.py
+++ b/tempest/api/identity/admin/v3/test_default_project_id.py
@@ -18,7 +18,6 @@
 
 
 class TestDefaultProjectId (base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
@@ -74,8 +73,7 @@
                                            domain_name=dom_name)
         auth_provider = auth.KeystoneV3AuthProvider(creds)
         creds = auth_provider.fill_credentials()
-        admin_client = clients.Manager(interface=self._interface,
-                                       credentials=creds)
+        admin_client = clients.Manager(credentials=creds)
 
         # verify the user's token and see that it is scoped to the project
         token, auth_data = admin_client.auth_provider.get_auth()
diff --git a/tempest/api/identity/admin/v3/test_domains.py b/tempest/api/identity/admin/v3/test_domains.py
index c1bc705..0914674 100644
--- a/tempest/api/identity/admin/v3/test_domains.py
+++ b/tempest/api/identity/admin/v3/test_domains.py
@@ -20,7 +20,6 @@
 
 
 class DomainsTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     def _delete_domain(self, domain_id):
         # It is necessary to disable the domain before deleting,
@@ -62,10 +61,7 @@
         self.assertIsNotNone(domain['id'])
         self.assertEqual(d_name, domain['name'])
         self.assertEqual(d_desc, domain['description'])
-        if self._interface == "json":
-            self.assertEqual(True, domain['enabled'])
-        else:
-            self.assertEqual('true', str(domain['enabled']).lower())
+        self.assertEqual(True, domain['enabled'])
         new_desc = data_utils.rand_name('new-desc-')
         new_name = data_utils.rand_name('new-name-')
 
diff --git a/tempest/api/identity/admin/v3/test_endpoints.py b/tempest/api/identity/admin/v3/test_endpoints.py
index eed0eb5..2283c21 100644
--- a/tempest/api/identity/admin/v3/test_endpoints.py
+++ b/tempest/api/identity/admin/v3/test_endpoints.py
@@ -19,7 +19,6 @@
 
 
 class EndPointsTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_endpoints_negative.py b/tempest/api/identity/admin/v3/test_endpoints_negative.py
index 9da0a57..9846010 100644
--- a/tempest/api/identity/admin/v3/test_endpoints_negative.py
+++ b/tempest/api/identity/admin/v3/test_endpoints_negative.py
@@ -22,7 +22,6 @@
 
 
 class EndpointsNegativeTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_groups.py b/tempest/api/identity/admin/v3/test_groups.py
index d8c7063..6dfddb0 100644
--- a/tempest/api/identity/admin/v3/test_groups.py
+++ b/tempest/api/identity/admin/v3/test_groups.py
@@ -19,7 +19,6 @@
 
 
 class GroupsV3TestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_list_projects.py b/tempest/api/identity/admin/v3/test_list_projects.py
index c0187f9..24b130c 100644
--- a/tempest/api/identity/admin/v3/test_list_projects.py
+++ b/tempest/api/identity/admin/v3/test_list_projects.py
@@ -19,7 +19,6 @@
 
 
 class ListProjectsTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_list_users.py b/tempest/api/identity/admin/v3/test_list_users.py
index e728867..a6c3309 100644
--- a/tempest/api/identity/admin/v3/test_list_users.py
+++ b/tempest/api/identity/admin/v3/test_list_users.py
@@ -19,7 +19,6 @@
 
 
 class UsersV3TestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     def _list_users_with_params(self, params, key, expected, not_expected):
         # Helper method to list users filtered with params and
diff --git a/tempest/api/identity/admin/v3/test_policies.py b/tempest/api/identity/admin/v3/test_policies.py
index 23df13d..0d5dc47 100644
--- a/tempest/api/identity/admin/v3/test_policies.py
+++ b/tempest/api/identity/admin/v3/test_policies.py
@@ -19,7 +19,6 @@
 
 
 class PoliciesTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     def _delete_policy(self, policy_id):
         self.policy_client.delete_policy(policy_id)
diff --git a/tempest/api/identity/admin/v3/test_projects.py b/tempest/api/identity/admin/v3/test_projects.py
index 2cf6458..d879c7a 100644
--- a/tempest/api/identity/admin/v3/test_projects.py
+++ b/tempest/api/identity/admin/v3/test_projects.py
@@ -19,7 +19,6 @@
 
 
 class ProjectsTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @test.attr(type='gate')
     def test_project_create_with_description(self):
diff --git a/tempest/api/identity/admin/v3/test_projects_negative.py b/tempest/api/identity/admin/v3/test_projects_negative.py
index 23a16d1..fc013c5 100644
--- a/tempest/api/identity/admin/v3/test_projects_negative.py
+++ b/tempest/api/identity/admin/v3/test_projects_negative.py
@@ -22,7 +22,6 @@
 
 
 class ProjectsNegativeTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @test.attr(type=['negative', 'gate'])
     def test_list_projects_by_unauthorized_user(self):
diff --git a/tempest/api/identity/admin/v3/test_regions.py b/tempest/api/identity/admin/v3/test_regions.py
index 2ca3538..359c0cf 100644
--- a/tempest/api/identity/admin/v3/test_regions.py
+++ b/tempest/api/identity/admin/v3/test_regions.py
@@ -21,7 +21,6 @@
 
 
 class RegionsTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_roles.py b/tempest/api/identity/admin/v3/test_roles.py
index b8b309d..15ca21e 100644
--- a/tempest/api/identity/admin/v3/test_roles.py
+++ b/tempest/api/identity/admin/v3/test_roles.py
@@ -19,7 +19,6 @@
 
 
 class RolesV3TestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/identity/admin/v3/test_services.py b/tempest/api/identity/admin/v3/test_services.py
index c060094..13e6d66 100644
--- a/tempest/api/identity/admin/v3/test_services.py
+++ b/tempest/api/identity/admin/v3/test_services.py
@@ -21,7 +21,6 @@
 
 
 class ServicesTestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     def _del_service(self, service_id):
         # Used for deleting the services created in this class
diff --git a/tempest/api/identity/admin/v3/test_tokens.py b/tempest/api/identity/admin/v3/test_tokens.py
index de142e0..36be098 100644
--- a/tempest/api/identity/admin/v3/test_tokens.py
+++ b/tempest/api/identity/admin/v3/test_tokens.py
@@ -21,7 +21,6 @@
 
 
 class TokensV3TestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @test.attr(type='smoke')
     def test_tokens(self):
diff --git a/tempest/api/identity/admin/v3/test_trusts.py b/tempest/api/identity/admin/v3/test_trusts.py
index 13c47eb..6107265 100644
--- a/tempest/api/identity/admin/v3/test_trusts.py
+++ b/tempest/api/identity/admin/v3/test_trusts.py
@@ -93,9 +93,7 @@
             username=self.trustor_username,
             password=self.trustor_password,
             tenant_name=self.trustor_project_name)
-        os = clients.Manager(
-            credentials=creds,
-            interface=self._interface)
+        os = clients.Manager(credentials=creds)
         self.trustor_client = os.identity_v3_client
 
     def cleanup_user_and_roles(self):
@@ -187,7 +185,6 @@
 
 
 class TrustsV3TestJSON(BaseTrustsV3Test):
-    _interface = 'json'
 
     def setUp(self):
         super(TrustsV3TestJSON, self).setUp()
diff --git a/tempest/api/identity/admin/v3/test_users.py b/tempest/api/identity/admin/v3/test_users.py
index 4f3ec05..2481d9d 100644
--- a/tempest/api/identity/admin/v3/test_users.py
+++ b/tempest/api/identity/admin/v3/test_users.py
@@ -19,7 +19,6 @@
 
 
 class UsersV3TestJSON(base.BaseIdentityV3AdminTest):
-    _interface = 'json'
 
     @test.attr(type='gate')
     def test_user_update(self):
diff --git a/tempest/api/identity/base.py b/tempest/api/identity/base.py
index 90e1a9e..7521823 100644
--- a/tempest/api/identity/base.py
+++ b/tempest/api/identity/base.py
@@ -31,8 +31,8 @@
     @classmethod
     def resource_setup(cls):
         super(BaseIdentityAdminTest, cls).resource_setup()
-        cls.os_adm = clients.AdminManager(interface=cls._interface)
-        cls.os = clients.Manager(interface=cls._interface)
+        cls.os_adm = clients.AdminManager()
+        cls.os = clients.Manager()
 
     @classmethod
     def disable_user(cls, user_name):
diff --git a/tempest/api/identity/test_extension.py b/tempest/api/identity/test_extension.py
index e3badfc..bbc4c13 100644
--- a/tempest/api/identity/test_extension.py
+++ b/tempest/api/identity/test_extension.py
@@ -18,7 +18,6 @@
 
 
 class ExtensionTestJSON(base.BaseIdentityV2AdminTest):
-    _interface = 'json'
 
     @test.attr(type='gate')
     def test_list_extensions(self):
diff --git a/tempest/api/image/base.py b/tempest/api/image/base.py
index 4d33d37..344742b 100644
--- a/tempest/api/image/base.py
+++ b/tempest/api/image/base.py
@@ -35,7 +35,6 @@
         cls.set_network_resources()
         super(BaseImageTest, cls).resource_setup()
         cls.created_images = []
-        cls._interface = 'json'
         cls.isolated_creds = credentials.get_isolated_credentials(
             cls.__name__, network_resources=cls.network_resources)
         if not CONF.service_available.glance:
diff --git a/tempest/api/image/v2/test_images_member.py b/tempest/api/image/v2/test_images_member.py
index ec1cf14..956829e 100644
--- a/tempest/api/image/v2/test_images_member.py
+++ b/tempest/api/image/v2/test_images_member.py
@@ -15,7 +15,6 @@
 
 
 class ImagesMemberTest(base.BaseV2MemberImageTest):
-    _interface = 'json'
 
     @test.attr(type='gate')
     def test_image_share_accept(self):
diff --git a/tempest/api/image/v2/test_images_member_negative.py b/tempest/api/image/v2/test_images_member_negative.py
index 9965286..4402af9 100644
--- a/tempest/api/image/v2/test_images_member_negative.py
+++ b/tempest/api/image/v2/test_images_member_negative.py
@@ -18,7 +18,6 @@
 
 
 class ImagesMemberNegativeTest(base.BaseV2MemberImageTest):
-    _interface = 'json'
 
     @test.attr(type=['negative', 'gate'])
     def test_image_share_invalid_status(self):
diff --git a/tempest/api/messaging/test_claims.py b/tempest/api/messaging/test_claims.py
index 1aab8d2..c9064b0 100644
--- a/tempest/api/messaging/test_claims.py
+++ b/tempest/api/messaging/test_claims.py
@@ -29,7 +29,6 @@
 
 
 class TestClaims(base.BaseMessagingTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/messaging/test_messages.py b/tempest/api/messaging/test_messages.py
index 3c27ac2..dca95fc 100644
--- a/tempest/api/messaging/test_messages.py
+++ b/tempest/api/messaging/test_messages.py
@@ -26,7 +26,6 @@
 
 
 class TestMessages(base.BaseMessagingTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/messaging/test_queues.py b/tempest/api/messaging/test_queues.py
index 04ba8a3..24656bf 100644
--- a/tempest/api/messaging/test_queues.py
+++ b/tempest/api/messaging/test_queues.py
@@ -48,7 +48,6 @@
 
 
 class TestManageQueue(base.BaseMessagingTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/admin/test_agent_management.py b/tempest/api/network/admin/test_agent_management.py
index e7fd016..20948cc 100644
--- a/tempest/api/network/admin/test_agent_management.py
+++ b/tempest/api/network/admin/test_agent_management.py
@@ -18,7 +18,6 @@
 
 
 class AgentManagementTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/admin/test_dhcp_agent_scheduler.py b/tempest/api/network/admin/test_dhcp_agent_scheduler.py
index a89f25c..4eb6b87 100644
--- a/tempest/api/network/admin/test_dhcp_agent_scheduler.py
+++ b/tempest/api/network/admin/test_dhcp_agent_scheduler.py
@@ -17,7 +17,6 @@
 
 
 class DHCPAgentSchedulersTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/admin/test_external_network_extension.py b/tempest/api/network/admin/test_external_network_extension.py
index 06cce48..6e24f8e 100644
--- a/tempest/api/network/admin/test_external_network_extension.py
+++ b/tempest/api/network/admin/test_external_network_extension.py
@@ -15,7 +15,6 @@
 
 
 class ExternalNetworksTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/admin/test_external_networks_negative.py b/tempest/api/network/admin/test_external_networks_negative.py
index 8eb6888..aa8dd9a 100644
--- a/tempest/api/network/admin/test_external_networks_negative.py
+++ b/tempest/api/network/admin/test_external_networks_negative.py
@@ -23,7 +23,6 @@
 
 
 class ExternalNetworksAdminNegativeTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     @test.attr(type=['negative'])
     def test_create_port_with_precreated_floatingip_as_fixed_ip(self):
diff --git a/tempest/api/network/admin/test_floating_ips_admin_actions.py b/tempest/api/network/admin/test_floating_ips_admin_actions.py
index 62ba1b3..ee3b0bb 100644
--- a/tempest/api/network/admin/test_floating_ips_admin_actions.py
+++ b/tempest/api/network/admin/test_floating_ips_admin_actions.py
@@ -22,7 +22,7 @@
 
 
 class FloatingIPAdminTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
+
     force_tenant_isolation = True
 
     @classmethod
diff --git a/tempest/api/network/admin/test_l3_agent_scheduler.py b/tempest/api/network/admin/test_l3_agent_scheduler.py
index a6de581..05a8e35 100644
--- a/tempest/api/network/admin/test_l3_agent_scheduler.py
+++ b/tempest/api/network/admin/test_l3_agent_scheduler.py
@@ -18,7 +18,6 @@
 
 
 class L3AgentSchedulerTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/admin/test_lbaas_agent_scheduler.py b/tempest/api/network/admin/test_lbaas_agent_scheduler.py
index da1af36..8cfd5c2 100644
--- a/tempest/api/network/admin/test_lbaas_agent_scheduler.py
+++ b/tempest/api/network/admin/test_lbaas_agent_scheduler.py
@@ -18,7 +18,6 @@
 
 
 class LBaaSAgentSchedulerTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/admin/test_load_balancer_admin_actions.py b/tempest/api/network/admin/test_load_balancer_admin_actions.py
index e81616b..2537b28 100644
--- a/tempest/api/network/admin/test_load_balancer_admin_actions.py
+++ b/tempest/api/network/admin/test_load_balancer_admin_actions.py
@@ -19,7 +19,6 @@
 
 
 class LoadBalancerAdminTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     """
     Test admin actions for load balancer.
diff --git a/tempest/api/network/admin/test_quotas.py b/tempest/api/network/admin/test_quotas.py
index f8dfca9..39850f5 100644
--- a/tempest/api/network/admin/test_quotas.py
+++ b/tempest/api/network/admin/test_quotas.py
@@ -20,7 +20,6 @@
 
 
 class QuotasTest(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/base.py b/tempest/api/network/base.py
index 520bec7..4cb1485 100644
--- a/tempest/api/network/base.py
+++ b/tempest/api/network/base.py
@@ -50,7 +50,6 @@
         neutron as True
     """
 
-    _interface = 'json'
     force_tenant_isolation = False
 
     # Default to ipv4.
@@ -421,8 +420,7 @@
 
         try:
             creds = cls.isolated_creds.get_admin_creds()
-            cls.os_adm = clients.Manager(
-                credentials=creds, interface=cls._interface)
+            cls.os_adm = clients.Manager(credentials=creds)
         except NotImplementedError:
             msg = ("Missing Administrative Network API credentials "
                    "in configuration.")
diff --git a/tempest/api/network/test_allowed_address_pair.py b/tempest/api/network/test_allowed_address_pair.py
index 57887ac..a4954af 100644
--- a/tempest/api/network/test_allowed_address_pair.py
+++ b/tempest/api/network/test_allowed_address_pair.py
@@ -23,7 +23,6 @@
 
 
 class AllowedAddressPairTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the Neutron Allowed Address Pair API extension using the Tempest
diff --git a/tempest/api/network/test_extensions.py b/tempest/api/network/test_extensions.py
index 54c3cb9..2b4ccaf 100644
--- a/tempest/api/network/test_extensions.py
+++ b/tempest/api/network/test_extensions.py
@@ -19,7 +19,6 @@
 
 
 class ExtensionsTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/test_extra_dhcp_options.py b/tempest/api/network/test_extra_dhcp_options.py
index bd70323..1faac58 100644
--- a/tempest/api/network/test_extra_dhcp_options.py
+++ b/tempest/api/network/test_extra_dhcp_options.py
@@ -19,7 +19,6 @@
 
 
 class ExtraDHCPOptionsTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations with the Extra DHCP Options Neutron API
diff --git a/tempest/api/network/test_floating_ips.py b/tempest/api/network/test_floating_ips.py
index 1151c5d..43b296c 100644
--- a/tempest/api/network/test_floating_ips.py
+++ b/tempest/api/network/test_floating_ips.py
@@ -24,7 +24,6 @@
 
 
 class FloatingIPTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Quantum API using the REST client for
diff --git a/tempest/api/network/test_floating_ips_negative.py b/tempest/api/network/test_floating_ips_negative.py
index 7e91ba2..81eedd4 100644
--- a/tempest/api/network/test_floating_ips_negative.py
+++ b/tempest/api/network/test_floating_ips_negative.py
@@ -26,7 +26,7 @@
 
 
 class FloatingIPNegativeTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
+
     """
     Test the following negative  operations for floating ips:
 
diff --git a/tempest/api/network/test_fwaas_extensions.py b/tempest/api/network/test_fwaas_extensions.py
index b0318c9..280c5bb 100644
--- a/tempest/api/network/test_fwaas_extensions.py
+++ b/tempest/api/network/test_fwaas_extensions.py
@@ -24,7 +24,6 @@
 
 
 class FWaaSExtensionTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/test_load_balancer.py b/tempest/api/network/test_load_balancer.py
index df76757..107d8cd 100644
--- a/tempest/api/network/test_load_balancer.py
+++ b/tempest/api/network/test_load_balancer.py
@@ -21,7 +21,6 @@
 
 
 class LoadBalancerTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/test_metering_extensions.py b/tempest/api/network/test_metering_extensions.py
index 6ba1ea4..c80d0e9 100644
--- a/tempest/api/network/test_metering_extensions.py
+++ b/tempest/api/network/test_metering_extensions.py
@@ -24,7 +24,6 @@
 
 
 class MeteringTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/test_networks.py b/tempest/api/network/test_networks.py
index a5f9667..0df455e 100644
--- a/tempest/api/network/test_networks.py
+++ b/tempest/api/network/test_networks.py
@@ -27,7 +27,6 @@
 
 
 class NetworksTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
@@ -399,7 +398,6 @@
 
 
 class BulkNetworkOpsTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/network/test_networks_negative.py b/tempest/api/network/test_networks_negative.py
index b694728..09bd9c3 100644
--- a/tempest/api/network/test_networks_negative.py
+++ b/tempest/api/network/test_networks_negative.py
@@ -22,7 +22,6 @@
 
 
 class NetworksNegativeTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     @test.attr(type=['negative', 'smoke'])
     def test_show_non_existent_network(self):
diff --git a/tempest/api/network/test_ports.py b/tempest/api/network/test_ports.py
index bf85e90..2460092 100644
--- a/tempest/api/network/test_ports.py
+++ b/tempest/api/network/test_ports.py
@@ -27,7 +27,6 @@
 
 
 class PortsTestJSON(sec_base.BaseSecGroupTest):
-    _interface = 'json'
 
     """
     Test the following operations for ports:
@@ -300,7 +299,6 @@
 
 
 class PortsAdminExtendedAttrsTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/test_routers.py b/tempest/api/network/test_routers.py
index 210a8af..b0ee00d 100644
--- a/tempest/api/network/test_routers.py
+++ b/tempest/api/network/test_routers.py
@@ -25,7 +25,6 @@
 
 
 class RoutersTest(base.BaseRouterTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/test_routers_negative.py b/tempest/api/network/test_routers_negative.py
index 32dcf74..655fa58 100644
--- a/tempest/api/network/test_routers_negative.py
+++ b/tempest/api/network/test_routers_negative.py
@@ -26,7 +26,6 @@
 
 
 class RoutersNegativeTest(base.BaseRouterTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/test_security_groups.py b/tempest/api/network/test_security_groups.py
index 415dedd..3d26b48 100644
--- a/tempest/api/network/test_security_groups.py
+++ b/tempest/api/network/test_security_groups.py
@@ -24,7 +24,7 @@
 
 
 class SecGroupTest(base.BaseSecGroupTest):
-    _interface = 'json'
+
     _tenant_network_cidr = CONF.network.tenant_network_cidr
 
     @classmethod
diff --git a/tempest/api/network/test_security_groups_negative.py b/tempest/api/network/test_security_groups_negative.py
index 0398c66..47b218c 100644
--- a/tempest/api/network/test_security_groups_negative.py
+++ b/tempest/api/network/test_security_groups_negative.py
@@ -26,7 +26,7 @@
 
 
 class NegativeSecGroupTest(base.BaseSecGroupTest):
-    _interface = 'json'
+
     _tenant_network_cidr = CONF.network.tenant_network_cidr
 
     @classmethod
diff --git a/tempest/api/network/test_service_type_management.py b/tempest/api/network/test_service_type_management.py
index 0492fe3..e620ae6 100644
--- a/tempest/api/network/test_service_type_management.py
+++ b/tempest/api/network/test_service_type_management.py
@@ -17,7 +17,6 @@
 
 
 class ServiceTypeManagementTestJSON(base.BaseNetworkTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/network/test_vpnaas_extensions.py b/tempest/api/network/test_vpnaas_extensions.py
index 9ff406c..d869b55 100644
--- a/tempest/api/network/test_vpnaas_extensions.py
+++ b/tempest/api/network/test_vpnaas_extensions.py
@@ -24,7 +24,6 @@
 
 
 class VPNaaSTestJSON(base.BaseAdminNetworkTest):
-    _interface = 'json'
 
     """
     Tests the following operations in the Neutron API using the REST client for
diff --git a/tempest/api/orchestration/base.py b/tempest/api/orchestration/base.py
index 2a99630..6873756 100644
--- a/tempest/api/orchestration/base.py
+++ b/tempest/api/orchestration/base.py
@@ -59,7 +59,7 @@
     @classmethod
     def _get_identity_admin_client(cls):
         """Returns an instance of the Identity Admin API client."""
-        manager = clients.AdminManager(interface=cls._interface)
+        manager = clients.AdminManager()
         admin_client = manager.identity_client
         return admin_client
 
diff --git a/tempest/api/telemetry/test_telemetry_alarming_api.py b/tempest/api/telemetry/test_telemetry_alarming_api.py
index 2457438..05aed08 100644
--- a/tempest/api/telemetry/test_telemetry_alarming_api.py
+++ b/tempest/api/telemetry/test_telemetry_alarming_api.py
@@ -18,7 +18,6 @@
 
 
 class TelemetryAlarmingAPITestJSON(base.BaseTelemetryTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/telemetry/test_telemetry_notification_api.py b/tempest/api/telemetry/test_telemetry_notification_api.py
index 7e5d6ee..147020e 100644
--- a/tempest/api/telemetry/test_telemetry_notification_api.py
+++ b/tempest/api/telemetry/test_telemetry_notification_api.py
@@ -21,7 +21,6 @@
 
 
 class TelemetryNotificationAPITestJSON(base.BaseTelemetryTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/admin/test_multi_backend.py b/tempest/api/volume/admin/test_multi_backend.py
index 65c4bd3..245161a 100644
--- a/tempest/api/volume/admin/test_multi_backend.py
+++ b/tempest/api/volume/admin/test_multi_backend.py
@@ -22,7 +22,6 @@
 
 
 class VolumeMultiBackendV2Test(base.BaseVolumeAdminTest):
-    _interface = "json"
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/admin/test_snapshots_actions.py b/tempest/api/volume/admin/test_snapshots_actions.py
index 6c64298..e7d9d7b 100644
--- a/tempest/api/volume/admin/test_snapshots_actions.py
+++ b/tempest/api/volume/admin/test_snapshots_actions.py
@@ -19,7 +19,6 @@
 
 
 class SnapshotsActionsV2Test(base.BaseVolumeAdminTest):
-    _interface = "json"
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/admin/test_volume_hosts.py b/tempest/api/volume/admin/test_volume_hosts.py
index a214edf..8189aab 100644
--- a/tempest/api/volume/admin/test_volume_hosts.py
+++ b/tempest/api/volume/admin/test_volume_hosts.py
@@ -18,7 +18,6 @@
 
 
 class VolumeHostsAdminV2TestsJSON(base.BaseVolumeAdminTest):
-    _interface = "json"
 
     @test.attr(type='gate')
     def test_list_hosts(self):
diff --git a/tempest/api/volume/admin/test_volume_quotas.py b/tempest/api/volume/admin/test_volume_quotas.py
index 52f2d90..2a30b54 100644
--- a/tempest/api/volume/admin/test_volume_quotas.py
+++ b/tempest/api/volume/admin/test_volume_quotas.py
@@ -23,7 +23,6 @@
 
 
 class BaseVolumeQuotasAdminV2TestJSON(base.BaseVolumeAdminTest):
-    _interface = "json"
     force_tenant_isolation = True
 
     @classmethod
diff --git a/tempest/api/volume/admin/test_volume_quotas_negative.py b/tempest/api/volume/admin/test_volume_quotas_negative.py
index d5eb05a..f972457 100644
--- a/tempest/api/volume/admin/test_volume_quotas_negative.py
+++ b/tempest/api/volume/admin/test_volume_quotas_negative.py
@@ -20,7 +20,6 @@
 
 
 class BaseVolumeQuotasNegativeV2TestJSON(base.BaseVolumeAdminTest):
-    _interface = "json"
     force_tenant_isolation = True
 
     @classmethod
diff --git a/tempest/api/volume/admin/test_volume_services.py b/tempest/api/volume/admin/test_volume_services.py
index 46db70f..3bab185 100644
--- a/tempest/api/volume/admin/test_volume_services.py
+++ b/tempest/api/volume/admin/test_volume_services.py
@@ -22,7 +22,6 @@
     Tests Volume Services API.
     volume service list requires admin privileges.
     """
-    _interface = "json"
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/admin/test_volume_types.py b/tempest/api/volume/admin/test_volume_types.py
index 58f1551..f2c1dda 100644
--- a/tempest/api/volume/admin/test_volume_types.py
+++ b/tempest/api/volume/admin/test_volume_types.py
@@ -22,7 +22,6 @@
 
 
 class VolumeTypesV2Test(base.BaseVolumeAdminTest):
-    _interface = "json"
 
     def _delete_volume(self, volume_id):
         self.volumes_client.delete_volume(volume_id)
diff --git a/tempest/api/volume/admin/test_volume_types_extra_specs.py b/tempest/api/volume/admin/test_volume_types_extra_specs.py
index 460a6c3..1ce1402 100644
--- a/tempest/api/volume/admin/test_volume_types_extra_specs.py
+++ b/tempest/api/volume/admin/test_volume_types_extra_specs.py
@@ -19,7 +19,6 @@
 
 
 class VolumeTypesExtraSpecsV2Test(base.BaseVolumeAdminTest):
-    _interface = "json"
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/admin/test_volume_types_extra_specs_negative.py b/tempest/api/volume/admin/test_volume_types_extra_specs_negative.py
index 2e2cfd2..2f3b382 100644
--- a/tempest/api/volume/admin/test_volume_types_extra_specs_negative.py
+++ b/tempest/api/volume/admin/test_volume_types_extra_specs_negative.py
@@ -24,7 +24,6 @@
 
 
 class ExtraSpecsNegativeV2Test(base.BaseVolumeAdminTest):
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/admin/test_volume_types_negative.py b/tempest/api/volume/admin/test_volume_types_negative.py
index 18d54fa..77ca34c 100644
--- a/tempest/api/volume/admin/test_volume_types_negative.py
+++ b/tempest/api/volume/admin/test_volume_types_negative.py
@@ -23,7 +23,6 @@
 
 
 class VolumeTypesNegativeV2Test(base.BaseVolumeAdminTest):
-    _interface = 'json'
 
     @test.attr(type='gate')
     def test_create_with_nonexistent_volume_type(self):
diff --git a/tempest/api/volume/admin/test_volumes_actions.py b/tempest/api/volume/admin/test_volumes_actions.py
index 4feba73..439dd35 100644
--- a/tempest/api/volume/admin/test_volumes_actions.py
+++ b/tempest/api/volume/admin/test_volumes_actions.py
@@ -19,7 +19,6 @@
 
 
 class VolumesActionsV2Test(base.BaseVolumeAdminTest):
-    _interface = "json"
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/admin/test_volumes_backup.py b/tempest/api/volume/admin/test_volumes_backup.py
index 0739480..d572893 100644
--- a/tempest/api/volume/admin/test_volumes_backup.py
+++ b/tempest/api/volume/admin/test_volumes_backup.py
@@ -24,7 +24,6 @@
 
 
 class VolumesBackupsV2Test(base.BaseVolumeAdminTest):
-    _interface = "json"
 
     @classmethod
     def resource_setup(cls):
diff --git a/tempest/api/volume/base.py b/tempest/api/volume/base.py
index a1858de..2489b79 100644
--- a/tempest/api/volume/base.py
+++ b/tempest/api/volume/base.py
@@ -31,7 +31,6 @@
     """Base test case class for all Cinder API tests."""
 
     _api_version = 2
-    _interface = 'json'
 
     @classmethod
     def resource_setup(cls):
@@ -155,8 +154,7 @@
 
         try:
             cls.adm_creds = cls.isolated_creds.get_admin_creds()
-            cls.os_adm = clients.Manager(
-                credentials=cls.adm_creds, interface=cls._interface)
+            cls.os_adm = clients.Manager(credentials=cls.adm_creds)
         except NotImplementedError:
             msg = "Missing Volume Admin API credentials in configuration."
             raise cls.skipException(msg)
diff --git a/tempest/api/volume/test_volume_transfers.py b/tempest/api/volume/test_volume_transfers.py
index b2961bd..7451050 100644
--- a/tempest/api/volume/test_volume_transfers.py
+++ b/tempest/api/volume/test_volume_transfers.py
@@ -30,13 +30,11 @@
         super(VolumesV2TransfersTest, cls).resource_setup()
 
         # Add another tenant to test volume-transfer
-        cls.os_alt = clients.Manager(cls.isolated_creds.get_alt_creds(),
-                                     interface=cls._interface)
+        cls.os_alt = clients.Manager(cls.isolated_creds.get_alt_creds())
         # Add admin tenant to cleanup resources
         try:
             creds = cls.isolated_creds.get_admin_creds()
-            cls.os_adm = clients.Manager(
-                credentials=creds, interface=cls._interface)
+            cls.os_adm = clients.Manager(credentials=creds)
         except NotImplementedError:
             msg = "Missing Volume Admin API credentials in configuration."
             raise cls.skipException(msg)
diff --git a/tempest/auth.py b/tempest/auth.py
index 5820893..c0c67c0 100644
--- a/tempest/auth.py
+++ b/tempest/auth.py
@@ -38,18 +38,15 @@
     Provide authentication
     """
 
-    def __init__(self, credentials, interface=None):
+    def __init__(self, credentials):
         """
         :param credentials: credentials for authentication
-        :param interface: 'json' or 'xml'. Applicable for tempest client only
-            (deprecated: only json now supported)
         """
         credentials = self._convert_credentials(credentials)
         if self.check_credentials(credentials):
             self.credentials = credentials
         else:
             raise TypeError("Invalid credentials")
-        self.interface = 'json'
         self.cache = None
         self.alt_auth_data = None
         self.alt_part = None
@@ -62,10 +59,8 @@
             return credentials
 
     def __str__(self):
-        return "Creds :{creds}, interface: {interface}, " \
-               "cached auth data: {cache}".format(
-                   creds=self.credentials, interface=self.interface,
-                   cache=self.cache)
+        return "Creds :{creds}, cached auth data: {cache}".format(
+            creds=self.credentials, cache=self.cache)
 
     @abc.abstractmethod
     def _decorate_request(self, filters, method, url, headers=None, body=None,
@@ -201,8 +196,8 @@
 
     token_expiry_threshold = datetime.timedelta(seconds=60)
 
-    def __init__(self, credentials, interface=None):
-        super(KeystoneAuthProvider, self).__init__(credentials, interface)
+    def __init__(self, credentials):
+        super(KeystoneAuthProvider, self).__init__(credentials)
         self.auth_client = self._auth_client()
 
     def _decorate_request(self, filters, method, url, headers=None, body=None,
diff --git a/tempest/clients.py b/tempest/clients.py
index cbc6571..1836173 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -155,10 +155,7 @@
     }
     default_params_with_timeout_values.update(default_params)
 
-    def __init__(self, credentials=None, interface='json', service=None):
-        # Set interface and client type first
-        self.interface = interface
-        # super cares for credentials validation
+    def __init__(self, credentials=None, service=None):
         super(Manager, self).__init__(credentials=credentials)
 
         self._set_compute_clients()
@@ -376,9 +373,8 @@
     managed client objects
     """
 
-    def __init__(self, interface='json', service=None):
+    def __init__(self, service=None):
         super(AdminManager, self).__init__(
             credentials=cred_provider.get_configured_credentials(
                 'identity_admin'),
-            interface=interface,
             service=service)
diff --git a/tempest/cmd/verify_tempest_config.py b/tempest/cmd/verify_tempest_config.py
index 65a3a95..87f5ca6 100755
--- a/tempest/cmd/verify_tempest_config.py
+++ b/tempest/cmd/verify_tempest_config.py
@@ -327,7 +327,7 @@
         CONF_PARSER = moves.configparser.SafeConfigParser()
         CONF_PARSER.optionxform = str
         CONF_PARSER.readfp(conf_file)
-    os = clients.AdminManager(interface='json')
+    os = clients.AdminManager()
     services = check_service_availability(os, update)
     results = {}
     for service in ['nova', 'cinder', 'neutron', 'swift']:
diff --git a/tempest/common/cred_provider.py b/tempest/common/cred_provider.py
index 07fd03f..40c1ad7 100644
--- a/tempest/common/cred_provider.py
+++ b/tempest/common/cred_provider.py
@@ -68,8 +68,7 @@
 
 @six.add_metaclass(abc.ABCMeta)
 class CredentialProvider(object):
-    def __init__(self, name, interface='json', password='pass',
-                 network_resources=None):
+    def __init__(self, name, password='pass', network_resources=None):
         self.name = name
 
     @abc.abstractmethod
diff --git a/tempest/common/isolated_creds.py b/tempest/common/isolated_creds.py
index 5c2fa58..cee610d 100644
--- a/tempest/common/isolated_creds.py
+++ b/tempest/common/isolated_creds.py
@@ -29,15 +29,12 @@
 
 class IsolatedCreds(cred_provider.CredentialProvider):
 
-    def __init__(self, name, interface='json', password='pass',
-                 network_resources=None):
-        super(IsolatedCreds, self).__init__(name, interface, password,
-                                            network_resources)
+    def __init__(self, name, password='pass', network_resources=None):
+        super(IsolatedCreds, self).__init__(name, password, network_resources)
         self.network_resources = network_resources
         self.isolated_creds = {}
         self.isolated_net_resources = {}
         self.ports = []
-        self.interface = interface
         self.password = password
         self.identity_admin_client, self.network_admin_client = (
             self._get_admin_clients())
@@ -49,7 +46,7 @@
             identity
             network
         """
-        os = clients.AdminManager(interface=self.interface)
+        os = clients.AdminManager()
         return os.identity_client, os.network_client
 
     def _create_tenant(self, name, description):
diff --git a/tempest/manager.py b/tempest/manager.py
index 2b00e89..421d2de 100644
--- a/tempest/manager.py
+++ b/tempest/manager.py
@@ -64,5 +64,4 @@
                 'Credentials must be specified')
         auth_provider_class = self.get_auth_provider_class(credentials)
         return auth_provider_class(
-            interface=getattr(self, 'interface', None),
             credentials=credentials)
diff --git a/tempest/test.py b/tempest/test.py
index 28e1e2c..0c9cbfd 100644
--- a/tempest/test.py
+++ b/tempest/test.py
@@ -359,7 +359,7 @@
                                                    level=None))
 
     @classmethod
-    def get_client_manager(cls, interface=None):
+    def get_client_manager(cls):
         """
         Returns an OpenStack client manager
         """
@@ -373,12 +373,7 @@
             )
 
         creds = cls.isolated_creds.get_primary_creds()
-        params = dict(credentials=creds, service=cls._service)
-        if getattr(cls, '_interface', None):
-            interface = cls._interface
-        if interface:
-            params['interface'] = interface
-        os = clients.Manager(**params)
+        os = clients.Manager(credentials=creds, service=cls._service)
         return os
 
     @classmethod
@@ -394,8 +389,7 @@
         """
         Returns an instance of the Identity Admin API client
         """
-        os = clients.AdminManager(interface=cls._interface,
-                                  service=cls._service)
+        os = clients.AdminManager(service=cls._service)
         admin_client = os.identity_client
         return admin_client
 
@@ -436,8 +430,7 @@
         super(NegativeAutoTest, cls).setUpClass()
         os = cls.get_client_manager()
         cls.client = os.negative_client
-        os_admin = clients.AdminManager(interface=cls._interface,
-                                        service=cls._service)
+        os_admin = clients.AdminManager(service=cls._service)
         cls.admin_client = os_admin.negative_client
 
     @staticmethod
diff --git a/tempest/tests/negative/test_negative_auto_test.py b/tempest/tests/negative/test_negative_auto_test.py
index fb1da43..7a127cd 100644
--- a/tempest/tests/negative/test_negative_auto_test.py
+++ b/tempest/tests/negative/test_negative_auto_test.py
@@ -21,7 +21,6 @@
 
 class TestNegativeAutoTest(base.TestCase):
     # Fake entries
-    _interface = 'json'
     _service = 'compute'
 
     fake_input_desc = {"name": "list-flavors-with-detail",