test(lifecycle): add retries for transient failures

This update introduces tests for the lifecycle endpoint.

It verifies that transient private-network failures are retried with bounded backoff.

Additionally, it checks that a safe transport cause code is reported after retries are exhausted.

Author: VictoriousWealth

scripts/run-account-lifecycle-cron.test.mjs

@@ -1,7 +1,10 @@
 import assert from "node:assert/strict";
 import test from "node:test";
 
-import { lifecycleEndpoint } from "./run-account-lifecycle-cron.mjs";
+import {
+  invokeLifecycleEndpoint,
+  lifecycleEndpoint,
+} from "./run-account-lifecycle-cron.mjs";
 
 const CRON_SECRET = "a".repeat(32);
 const privateOriginWithCredentials = new URL(
@@ -67,3 +70,63 @@ test("still rejects insecure public fallback origins", () => {
     /APP_ORIGIN_MUST_USE_HTTPS/
   );
 });
+
+test("retries transient private-network failures with bounded backoff", async () => {
+  let attempts = 0;
+  const delays = [];
+  const response = await invokeLifecycleEndpoint(
+    lifecycleEndpoint({
+      ACCOUNT_LIFECYCLE_CRON_ORIGIN:
+        "http://study-buddy-v2.railway.internal:8080",
+      ACCOUNT_DELETION_CRON_SECRET: CRON_SECRET,
+    }),
+    {
+      fetchImpl: async () => {
+        attempts += 1;
+        if (attempts < 3) {
+          throw Object.assign(new TypeError("fetch failed"), {
+            cause: { code: "EAI_AGAIN" },
+          });
+        }
+        return { ok: true, status: 200 };
+      },
+      sleepImpl: async (delayMs) => delays.push(delayMs),
+      retryDelays: [0, 1_000, 3_000],
+      onRetry: () => {},
+    }
+  );
+
+  assert.equal(response.status, 200);
+  assert.equal(attempts, 3);
+  assert.deepEqual(delays, [1_000, 3_000]);
+});
+
+test("reports a safe transport cause code after retries are exhausted", async () => {
+  let attempts = 0;
+
+  await assert.rejects(
+    invokeLifecycleEndpoint(
+      lifecycleEndpoint({
+        ACCOUNT_LIFECYCLE_CRON_ORIGIN:
+          "http://study-buddy-v2.railway.internal:8080",
+        ACCOUNT_DELETION_CRON_SECRET: CRON_SECRET,
+      }),
+      {
+        fetchImpl: async () => {
+          attempts += 1;
+          throw Object.assign(new TypeError("fetch failed"), {
+            cause: { code: "ECONNREFUSED" },
+          });
+        },
+        sleepImpl: async () => {},
+        retryDelays: [0, 0],
+        onRetry: () => {},
+      }
+    ),
+    (error) =>
+      error?.reason === "TRANSPORT_FAILURE" &&
+      error?.causeCode === "ECONNREFUSED"
+  );
+
+  assert.equal(attempts, 2);
+});