diff --git a/swh/journal/tests/test_inmemory.py b/swh/journal/tests/test_inmemory.py
--- a/swh/journal/tests/test_inmemory.py
+++ b/swh/journal/tests/test_inmemory.py
@@ -3,6 +3,40 @@
 from swh.journal.writer import model_object_dict_sanitizer
 from swh.journal.writer.inmemory import InMemoryJournalWriter
 from swh.model.model import BaseModel
+from swh.model.tests.swh_model_data import TEST_OBJECTS
+
+
+def test_write_additions_with_test_objects():
+    writer = InMemoryJournalWriter[BaseModel](
+        value_sanitizer=model_object_dict_sanitizer
+    )
+    expected = []
+
+    for object_type, objects in TEST_OBJECTS.items():
+        writer.write_additions(object_type, objects)
+
+        for object in objects:
+            expected.append((object_type, object))
+
+    assert list(writer.privileged_objects) == []
+    assert set(expected) == set(writer.objects)
+
+
+def test_write_additions_with_privileged_test_objects():
+    writer = InMemoryJournalWriter[BaseModel](
+        value_sanitizer=model_object_dict_sanitizer
+    )
+
+    expected = []
+
+    for object_type, objects in TEST_OBJECTS.items():
+        writer.write_additions(object_type, objects, True)
+
+        for object in objects:
+            expected.append((object_type, object))
+
+    assert list(writer.objects) == []
+    assert set(expected) == set(writer.privileged_objects)
 
 
 def test_write_addition_errors_without_unique_key():