diff --git a/sql/upgrades/118.sql b/sql/upgrades/118.sql
--- a/sql/upgrades/118.sql
+++ b/sql/upgrades/118.sql
@@ -7,5 +7,7 @@
 values(118, now(), 'Work In Progress');
 
 alter table content_mimetype
-  alter column mimetype set data type text,
-  alter column encoding set data type text;
+  alter column mimetype set data type text
+    using convert_from(mimetype, 'utf-8'),
+  alter column encoding set data type text
+    using convert_from(encoding, 'utf-8');
diff --git a/swh/indexer/tests/test_origin_head.py b/swh/indexer/tests/test_origin_head.py
--- a/swh/indexer/tests/test_origin_head.py
+++ b/swh/indexer/tests/test_origin_head.py
@@ -4,18 +4,20 @@
 # See top-level LICENSE file for more information
 
 import unittest
-import logging
 
 from swh.indexer.origin_head import OriginHeadIndexer
-from swh.indexer.tests.test_utils import MockIndexerStorage, MockStorage
+from swh.indexer.tests.test_utils import (
+    MockIndexerStorage, MockStorage, BASE_TEST_CONFIG
+)
 
 
 class OriginHeadTestIndexer(OriginHeadIndexer):
     """Specific indexer whose configuration is enough to satisfy the
        indexing tests.
     """
-    def prepare(self):
-        self.config = {
+    def parse_config_file(self, *args, **kwargs):
+        return {
+            **BASE_TEST_CONFIG,
             'tools': {
                 'name': 'origin-metadata',
                 'version': '0.0.1',
@@ -26,13 +28,11 @@
                 'origin_intrinsic_metadata': None,
             }
         }
+
+    def prepare(self):
+        super().prepare()
         self.storage = MockStorage()
         self.idx_storage = MockIndexerStorage()
-        self.log = logging.getLogger('swh.indexer')
-        self.objstorage = None
-        self.tools = self.register_tools(self.config['tools'])
-        self.tool = self.tools[0]
-        self.results = None
 
     def persist_index_computations(self, results, policy_update):
         self.results = results
diff --git a/swh/indexer/tests/test_origin_metadata.py b/swh/indexer/tests/test_origin_metadata.py
--- a/swh/indexer/tests/test_origin_metadata.py
+++ b/swh/indexer/tests/test_origin_metadata.py
@@ -18,24 +18,21 @@
 
 from swh.model.hashutil import hash_to_bytes
 
+from .test_utils import BASE_TEST_CONFIG
+
 
 class OriginMetadataTestIndexer(OriginMetadataIndexer):
-    def prepare(self):
-        self.config = {
-            'storage': {
-                'cls': 'remote',
-                'args': {
-                    'url': 'http://localhost:9999',
-                }
-            },
+    def parse_config_file(self, *args, **kwargs):
+        return {
+            **BASE_TEST_CONFIG,
             'tools': [],
         }
+
+    def prepare(self):
+        super().prepare()
         self.storage = MockStorage()
         self.idx_storage = MockIndexerStorage()
-        self.log = logging.getLogger('swh.indexer')
         self.objstorage = MockObjStorage()
-        self.tools = self.register_tools(self.config['tools'])
-        self.results = []
 
 
 class ContentMetadataTestIndexer(ContentMetadataIndexer):