diff --git a/swh/journal/tests/test_client.py b/swh/journal/tests/test_client.py
new file mode 100644
--- /dev/null
+++ b/swh/journal/tests/test_client.py
@@ -0,0 +1,50 @@
+# Copyright (C) 2019 The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+from subprocess import Popen
+from typing import Tuple
+from unittest.mock import MagicMock
+
+from confluent_kafka import Producer
+
+from swh.model.hypothesis_strategies import revisions
+
+from swh.journal.client import JournalClient
+from swh.journal.serializers import key_to_kafka, value_to_kafka
+
+
+def test_client(
+        kafka_prefix: str,
+        kafka_server: Tuple[Popen, int]):
+    (_, port) = kafka_server
+    kafka_prefix += '.swh.journal.objects'
+
+    producer = Producer({
+        'bootstrap.servers': 'localhost:{}'.format(port),
+        'client.id': 'test producer',
+        'enable.idempotence': 'true',
+    })
+
+    rev = revisions().example()
+
+    # Fill Kafka
+    producer.produce(
+        topic=kafka_prefix + '.revision', key=key_to_kafka(rev.id),
+        value=value_to_kafka(rev.to_dict()),
+    )
+    producer.flush()
+
+    config = {
+        'brokers': 'localhost:%d' % kafka_server[1],
+        'group_id': 'replayer',
+        'prefix': kafka_prefix,
+        'max_messages': 1,
+    }
+    client = JournalClient(**config)
+
+    worker_fn = MagicMock()
+    client.process(worker_fn)
+
+    worker_fn.assert_called_once_with({'revision': [rev.to_dict()]})