diff --git a/src/documents/tests/test_api_document_versions.py b/src/documents/tests/test_api_document_versions.py
new file mode 100644
index 000000000..fec5c3b6d
--- /dev/null
+++ b/src/documents/tests/test_api_document_versions.py
@@ -0,0 +1,145 @@
+from __future__ import annotations
+
+from unittest import mock
+
+from django.contrib.auth.models import User
+from rest_framework import status
+from rest_framework.test import APITestCase
+
+from documents.models import Document
+from documents.tests.utils import DirectoriesMixin
+
+
+class TestDocumentVersioningApi(DirectoriesMixin, APITestCase):
+    def setUp(self) -> None:
+        super().setUp()
+
+        self.user = User.objects.create_superuser(username="temp_admin")
+        self.client.force_authenticate(user=self.user)
+
+    def test_root_endpoint_returns_root_for_version_and_root(self) -> None:
+        root = Document.objects.create(
+            title="root",
+            checksum="root",
+            mime_type="application/pdf",
+        )
+        version = Document.objects.create(
+            title="v1",
+            checksum="v1",
+            mime_type="application/pdf",
+            root_document=root,
+        )
+
+        resp_root = self.client.get(f"/api/documents/{root.id}/root/")
+        self.assertEqual(resp_root.status_code, status.HTTP_200_OK)
+        self.assertEqual(resp_root.data["root_id"], root.id)
+
+        resp_version = self.client.get(f"/api/documents/{version.id}/root/")
+        self.assertEqual(resp_version.status_code, status.HTTP_200_OK)
+        self.assertEqual(resp_version.data["root_id"], root.id)
+
+    def test_delete_version_disallows_deleting_root(self) -> None:
+        root = Document.objects.create(
+            title="root",
+            checksum="root",
+            mime_type="application/pdf",
+        )
+
+        with mock.patch("documents.index.remove_document_from_index"):
+            resp = self.client.delete(f"/api/documents/{root.id}/versions/{root.id}/")
+
+        self.assertEqual(resp.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertTrue(Document.objects.filter(id=root.id).exists())
+
+    def test_delete_version_deletes_version_and_returns_current_version(self) -> None:
+        root = Document.objects.create(
+            title="root",
+            checksum="root",
+            mime_type="application/pdf",
+        )
+        v1 = Document.objects.create(
+            title="v1",
+            checksum="v1",
+            mime_type="application/pdf",
+            root_document=root,
+        )
+        v2 = Document.objects.create(
+            title="v2",
+            checksum="v2",
+            mime_type="application/pdf",
+            root_document=root,
+        )
+
+        with mock.patch("documents.index.remove_document_from_index"):
+            resp = self.client.delete(f"/api/documents/{root.id}/versions/{v2.id}/")
+
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+        self.assertFalse(Document.objects.filter(id=v2.id).exists())
+        self.assertEqual(resp.data["current_version_id"], v1.id)
+
+        with mock.patch("documents.index.remove_document_from_index"):
+            resp = self.client.delete(f"/api/documents/{root.id}/versions/{v1.id}/")
+
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+        self.assertFalse(Document.objects.filter(id=v1.id).exists())
+        self.assertEqual(resp.data["current_version_id"], root.id)
+
+    def test_delete_version_writes_audit_log_entry(self) -> None:
+        root = Document.objects.create(
+            title="root",
+            checksum="root",
+            mime_type="application/pdf",
+        )
+        version = Document.objects.create(
+            title="v1",
+            checksum="v1",
+            mime_type="application/pdf",
+            root_document=root,
+        )
+        version_id = version.id
+
+        with mock.patch("documents.index.remove_document_from_index"):
+            resp = self.client.delete(
+                f"/api/documents/{root.id}/versions/{version_id}/",
+            )
+
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+
+        # Audit log entry is created against the root document.
+        from auditlog.models import LogEntry
+
+        entry = LogEntry.objects.get_for_object(root).order_by("-timestamp").first()
+        self.assertIsNotNone(entry)
+        assert entry is not None
+        self.assertEqual(entry.actor_id, self.user.id)
+        self.assertEqual(entry.action, LogEntry.Action.UPDATE)
+        self.assertEqual(
+            entry.changes,
+            {"Version Deleted": ["None", version_id]},
+        )
+        self.assertEqual(entry.additional_data.get("version_id"), version_id)
+
+    def test_delete_version_returns_404_when_version_not_related(self) -> None:
+        root = Document.objects.create(
+            title="root",
+            checksum="root",
+            mime_type="application/pdf",
+        )
+        other_root = Document.objects.create(
+            title="other",
+            checksum="other",
+            mime_type="application/pdf",
+        )
+        other_version = Document.objects.create(
+            title="other-v1",
+            checksum="other-v1",
+            mime_type="application/pdf",
+            root_document=other_root,
+        )
+
+        with mock.patch("documents.index.remove_document_from_index"):
+            resp = self.client.delete(
+                f"/api/documents/{root.id}/versions/{other_version.id}/",
+            )
+
+        self.assertEqual(resp.status_code, status.HTTP_404_NOT_FOUND)