diff --git a/test/unit/json-utils.test.ts b/test/unit/json-utils.test.ts
index 0a72ce1981..5d2d74b9ef 100644
--- a/test/unit/json-utils.test.ts
+++ b/test/unit/json-utils.test.ts
@@ -1,15 +1,22 @@
 import { describe, expect, it } from "vitest";
-import { errorMessage, jsonString, normalizeRepoFullName, parseJson, repoParts, strippedErrorMessage } from "../../src/utils/json";
+import { errorMessage, jsonString, normalizeRepoFullName, nowIso, parseJson, repoParts, strippedErrorMessage } from "../../src/utils/json";
 
 describe("JSON and string utility helpers", () => {
   it("keeps JSON parsing and stringification fallbacks explicit", () => {
     expect(parseJson<{ ok: boolean }>('{"ok":true}', { ok: false })).toEqual({ ok: true });
     expect(parseJson("{bad-json", { ok: false })).toEqual({ ok: false });
     expect(parseJson(null, { ok: false })).toEqual({ ok: false });
+    expect(parseJson("", { ok: false })).toEqual({ ok: false });
+    expect(parseJson(undefined, { ok: false })).toEqual({ ok: false });
     expect(jsonString(undefined)).toBe("null");
     expect(jsonString({ ok: true })).toBe('{"ok":true}');
   });
 
+  it("emits ISO timestamps and empty error fallbacks", () => {
+    expect(nowIso()).toMatch(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/);
+    expect(errorMessage(new Error(""))).toBe("unknown error");
+  });
+
   it("normalizes repo names and error messages without leaking arbitrary thrown values", () => {
     expect(normalizeRepoFullName(" JSONbored/gittensory ")).toBe("JSONbored/gittensory");
     expect(repoParts("JSONbored/gittensory")).toEqual({ owner: "JSONbored", name: "gittensory" });