diff --git a/swh/vault/tests/test_to_disk.py b/swh/vault/tests/test_to_disk.py
new file mode 100644
--- /dev/null
+++ b/swh/vault/tests/test_to_disk.py
@@ -0,0 +1,73 @@
+# Copyright (C) 2020  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 pytest
+
+from swh.model.model import Content, SkippedContent
+
+from swh.vault.to_disk import get_filtered_files_content
+
+
+def test_get_filtered_files_content(swh_storage):
+    content = Content.from_data(b"foo bar")
+    skipped_content = SkippedContent(
+        sha1=None,
+        sha1_git=b"c" * 20,
+        sha256=None,
+        blake2s256=None,
+        length=42,
+        status="absent",
+        reason="for some reason",
+    )
+    swh_storage.content_add([content])
+    swh_storage.skipped_content_add([skipped_content])
+
+    files_data = [
+        {
+            "status": "visible",
+            "sha1": content.sha1,
+            "sha1_git": content.sha1_git,
+            "target": content.sha1_git,
+        },
+        {"status": "absent", "target": skipped_content.sha1_git,},
+    ]
+
+    res = list(get_filtered_files_content(swh_storage, files_data))
+
+    assert res == [
+        {
+            "content": content.data,
+            "status": "visible",
+            "sha1": content.sha1,
+            "sha1_git": content.sha1_git,
+            "target": content.sha1_git,
+        },
+        {
+            "content": (
+                b"This content has not been retrieved in the "
+                b"Software Heritage archive due to its size."
+            ),
+            "status": "absent",
+            "target": skipped_content.sha1_git,
+        },
+    ]
+
+
+def test_get_filtered_files_content__unknown_status(swh_storage):
+    content = Content.from_data(b"foo bar")
+    swh_storage.content_add([content])
+
+    files_data = [
+        {
+            "status": "visible",
+            "sha1": content.sha1,
+            "sha1_git": content.sha1_git,
+            "target": content.sha1_git,
+        },
+        {"status": None, "target": b"c" * 20,},
+    ]
+
+    with pytest.raises(AssertionError, match="unexpected status None"):
+        list(get_filtered_files_content(swh_storage, files_data))
diff --git a/swh/vault/to_disk.py b/swh/vault/to_disk.py
--- a/swh/vault/to_disk.py
+++ b/swh/vault/to_disk.py
@@ -55,6 +55,11 @@
                 content = SKIPPED_MESSAGE
             else:
                 content = data
+        else:
+            assert False, (
+                f"unexpected status {status!r} "
+                f"for content {hashutil.hash_to_hex(file_data['target'])}"
+            )
 
         yield {"content": content, **file_data}