Enhance tests for assignment create_grant when no user or group

There were no tests that show the behavior of create_grant when
the user or group doesn't exist. Turns out the behavior is
different depending on the backend (sql vs kvs vs ldap).

Change-Id: I71c3e2b94aaa44e40c8a891b49cc2a9961cee16f
Related-Bug: #1239476

keystone/tests/test_backend.py

@@ -2705,6 +2705,22 @@ def test_updated_arbitrary_attributes_are_returned_from_update_user(self):
 
         self.assertEqual(updated_user['arbitrary_attr'], new_attr_value)
 
+    def test_create_grant_no_user(self):
+        # If call create_grant with a user that doesn't exist, doesn't fail.
+        # The behavior is different depending on the backend, see bug #1239476.
+        self.assignment_api.create_grant(
+            self.role_other['id'],
+            user_id=uuid.uuid4().hex,
+            project_id=self.tenant_bar['id'])
+
+    def test_create_grant_no_group(self):
+        # If call create_grant with a group that doesn't exist, doesn't fail.
+        # The behavior is different depending on the backend, see bug #1239476.
+        self.assignment_api.create_grant(
+            self.role_other['id'],
+            group_id=uuid.uuid4().hex,
+            project_id=self.tenant_bar['id'])
+
 
 class TokenTests(object):
     def _create_token_id(self):

keystone/tests/test_backend_kvs.py

@@ -75,6 +75,20 @@ def test_delete_group_grant_no_group(self):
             exception.GroupNotFound,
             super(KvsIdentity, self).test_delete_group_grant_no_group)
 
+    def test_create_grant_no_user(self):
+        # If call create_grant on KVS backend with a user that doesn't exist,
+        # raises UserNotFound.
+        # The behavior is different depending on the backend, see bug #1239476.
+        self.assertRaises(exception.UserNotFound,
+                          super(KvsIdentity, self).test_create_grant_no_user)
+
+    def test_create_grant_no_group(self):
+        # If call create_grant on KVS backend with a group that doesn't exist,
+        # raises GroupNotFound.
+        # The behavior is different depending on the backend, see bug #1239476.
+        self.assertRaises(exception.GroupNotFound,
+                          super(KvsIdentity, self).test_create_grant_no_group)
+
 
 class KvsToken(tests.TestCase, test_backend.TokenTests):
     def setUp(self):

keystone/tests/test_backend_ldap.py

@@ -894,6 +894,18 @@ def test_list_projects_for_alternate_domain(self):
         self.skipTest(
             'N/A: LDAP does not support multiple domains')
 
+    def test_create_grant_no_user(self):
+        # The LDAP assignment backend doesn't implement create_grant.
+        self.assertRaises(
+            exception.NotImplemented,
+            super(BaseLDAPIdentity, self).test_create_grant_no_user)
+
+    def test_create_grant_no_group(self):
+        # The LDAP assignment backend doesn't implement create_grant.
+        self.assertRaises(
+            exception.NotImplemented,
+            super(BaseLDAPIdentity, self).test_create_grant_no_group)
+
 
 class LDAPIdentityEnabledEmulation(LDAPIdentity):
     def setUp(self):