diff --git a/tests/DownloadRouter.test.ts b/tests/DownloadRouter.test.ts
new file mode 100644
index 00000000..a7435050
--- /dev/null
+++ b/tests/DownloadRouter.test.ts
@@ -0,0 +1,46 @@
+import { handleDownloadCompletion } from '../src/routes/download/DownloadRouter'
+
+describe('backup download completion', () => {
+    test('returns 404 when the one-time backup file is already gone', () => {
+        const sendStatus = jest.fn()
+        const next = jest.fn()
+        const response = {
+            headersSent: false,
+            sendStatus,
+        }
+
+        const error = Object.assign(new Error('missing backup'), {
+            code: 'ENOENT',
+        })
+
+        handleDownloadCompletion(
+            error,
+            '/tmp/missing-caprover-backup.tar',
+            response as any,
+            next
+        )
+
+        expect(sendStatus).toHaveBeenCalledWith(404)
+        expect(next).not.toHaveBeenCalled()
+    })
+
+    test('delegates other transfer errors', () => {
+        const sendStatus = jest.fn()
+        const next = jest.fn()
+        const response = {
+            headersSent: false,
+            sendStatus,
+        }
+        const error = new Error('transfer failed')
+
+        handleDownloadCompletion(
+            error,
+            '/tmp/missing-caprover-backup.tar',
+            response as any,
+            next
+        )
+
+        expect(sendStatus).not.toHaveBeenCalled()
+        expect(next).toHaveBeenCalledWith(error)
+    })
+})