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 +3,45 @@
 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
+
+OBJECT_TYPE = "content"
+TEST_CONTENT = TEST_OBJECTS[OBJECT_TYPE]
+
+
+def test_write_additions_with_test_objects():
+    writer = InMemoryJournalWriter[BaseModel](
+        value_sanitizer=model_object_dict_sanitizer
+    )
+    writer.write_additions(OBJECT_TYPE, TEST_CONTENT)
+
+    expected = []
+    for content in TEST_CONTENT:
+        expected.append((OBJECT_TYPE, content))
+
+    assert sorted(expected, key=lambda x: x[1].swhid()) == sorted(
+        writer.objects, key=lambda x: x[1].swhid()
+    )
+
+    assert len(writer.privileged_objects) == 0
+
+
+def test_write_additions_with_privileged_test_objects():
+    writer = InMemoryJournalWriter[BaseModel](
+        value_sanitizer=model_object_dict_sanitizer
+    )
+
+    writer.write_additions(OBJECT_TYPE, TEST_CONTENT, True)
+
+    expected = []
+    for content in TEST_CONTENT:
+        expected.append((OBJECT_TYPE, content))
+
+    assert sorted(expected, key=lambda x: x[1].swhid()) == sorted(
+        writer.privileged_objects, key=lambda x: x[1].swhid()
+    )
+
+    assert len(writer.objects) == 0
 
 
 def test_write_addition_errors_without_unique_key():