diff --git a/app/test/releases.test.js b/app/test/releases.test.js
index 500b671..a55964b 100644
--- a/app/test/releases.test.js
+++ b/app/test/releases.test.js
@@ -27,6 +27,21 @@ test('selectReleasesToDelete 在 keepCount 為 0 時刪除全部(由新到舊)',
   )
 })
 
+test('selectReleasesToDelete 在 created_at 相同時以 id 決定順序(具決定性)', () => {
+  const same = '2024-01-01T00:00:00Z'
+  const list = [
+    { id: 1, created_at: same },
+    { id: 3, created_at: same },
+    { id: 2, created_at: same },
+  ]
+  const toDelete = selectReleasesToDelete(list, 1)
+  // 保留 id 最大者(3),刪除 id 2 與 1(順序固定)
+  assert.deepEqual(
+    toDelete.map((r) => r.id),
+    [2, 1],
+  )
+})
+
 test('selectReleasesToDelete 不改動原陣列', () => {
   const original = [...releases]
   selectReleasesToDelete(releases, 1)