Add assertOriginMetadataOk.

Test Plan

Has no proper test yet (#1393 (closed)). I'm going to send a diff that uses it for swh.deposit.

---

Migrated from D720 (view on Phabricator)

swh/loader/core/tests/__init__.py

@@ -132,6 +132,25 @@ class BaseLoaderStorageTest:
         }
         self.assertEqual(expected_branches, branches)
 
+    def assertOriginMetadataContains(self, origin_type, origin_url,
+                                     expected_origin_metadata):
+        """Checks the storage contains this metadata for the given origin.
+
+        Args:
+
+            origin_type (str): type of origin ('deposit', 'git', 'svn', ...)
+            origin_url (str): URL of the origin
+            expected_origin_metadata (dict):
+                              Extrinsic metadata of the origin
+                              <https://forge.softwareheritage.org/T1344>
+        """
+        origin = self.storage.origin_get(
+                dict(type=origin_type, url=origin_url))
+        results = self.storage.origin_metadata_get_by(origin)
+        self.assertEqual(len(results), 1, results)
+        result = results[0]
+        self.assertEqual(result['metadata'], expected_origin_metadata)
+
 
 @pytest.mark.fs
 class BaseLoaderTest(TestCase, BaseLoaderStorageTest):