diff --git a/swh/storage/tests/test_objstorage_multiplexer.py b/swh/storage/tests/test_objstorage_multiplexer.py
new file mode 100644
index 00000000..bd4bd07a
--- /dev/null
+++ b/swh/storage/tests/test_objstorage_multiplexer.py
@@ -0,0 +1,78 @@
+# Copyright (C) 2015-2016  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
+
+import tempfile
+import unittest
+
+from nose.tools import istest
+
+from swh.storage.objstorage import PathSlicingObjStorage
+from swh.storage.objstorage.multiplexer import MultiplexerObjStorage
+from swh.storage.objstorage.multiplexer.filter import add_filter, read_only
+
+from objstorage_testing import ObjStorageTestFixture
+
+
+class TestMultiplexerObjStorage(ObjStorageTestFixture, unittest.TestCase):
+
+    def setUp(self):
+        super().setUp()
+        self.storage_v1 = PathSlicingObjStorage(tempfile.mkdtemp(), '0:2/2:4')
+        self.storage_v2 = PathSlicingObjStorage(tempfile.mkdtemp(), '0:1/0:5')
+
+        self.r_storage = add_filter(self.storage_v1, read_only())
+        self.w_storage = self.storage_v2
+        self.storage = MultiplexerObjStorage([self.r_storage, self.w_storage])
+
+    @istest
+    def contains(self):
+        content_p, obj_id_p = self.hash_content(b'contains_present')
+        content_m, obj_id_m = self.hash_content(b'contains_missing')
+        self.storage.add(content_p, obj_id=obj_id_p)
+        self.assertIn(obj_id_p, self.storage)
+        self.assertNotIn(obj_id_m, self.storage)
+
+    @istest
+    def iter(self):
+        content, obj_id = self.hash_content(b'iter')
+        self.assertEqual(list(iter(self.storage)), [])
+        self.storage.add(content, obj_id=obj_id)
+        self.assertEqual(list(iter(self.storage)), [obj_id])
+
+    @istest
+    def len(self):
+        content, obj_id = self.hash_content(b'len')
+        self.assertEqual(len(self.storage), 0)
+        self.storage.add(content, obj_id=obj_id)
+        self.assertEqual(len(self.storage), 1)
+
+    @istest
+    def len_multiple(self):
+        content, obj_id = self.hash_content(b'len_multiple')
+        # Add a content to the read-only storage
+        self.storage_v1.add(content)
+        self.assertEqual(len(self.storage), 1)
+        # By adding the same content to the global storage, it should be
+        # Replicated.
+        # len() behavior is to indicates the number of files, not unique
+        # contents.
+        self.storage.add(content)
+        self.assertEqual(len(self.storage), 2)
+
+    @istest
+    def get_random_contents(self):
+        content, obj_id = self.hash_content(b'get_random_content')
+        self.storage.add(content)
+        random_contents = list(self.storage.get_random(1))
+        self.assertEqual(1, len(random_contents))
+        self.assertIn(obj_id, random_contents)
+
+    @istest
+    def access_readonly(self):
+        # Add a content to the readonly storage
+        content, obj_id = self.hash_content(b'content in read-only')
+        self.storage_v1.add(content)
+        # Try to retrieve it on the main storage
+        self.assertIn(obj_id, self.storage)