test(FN-4847): complete Step 4 — add denial-reason contract backstop

Fusion-Task-Id: FN-4847
Fusion-Task-Lineage: af551b65-a484-496a-8bab-b46193e06104

packages/engine/src/__tests__/reliability-interactions/node-settings-sync-auth.test.ts

@@ -0,0 +1,18 @@
+import { describe, expect, it } from "vitest";
+import { ApiError } from "../../../../dashboard/src/api-error.ts";
+import {
+  SYNC_STATUS_DENIAL_REASONS,
+  classifySyncStatusDenialReason,
+} from "../../../../dashboard/src/routes/register-settings-sync-helpers.js";
+
+// This contract test fails loudly if dashboard denial-reason enum values change without updating cross-node consumers.
+describe("reliability: node settings sync auth denial-reason contract", () => {
+  it("pins the SyncStatusDenialReason enum values consumed by cross-node sync-status callers", () => {
+    expect(SYNC_STATUS_DENIAL_REASONS).toEqual(["missing-remote-api-key", "auth-failed", "unreachable", "unknown"]);
+
+    expect(classifySyncStatusDenialReason(new ApiError(400, "Remote node requires an apiKey for authenticated sync"))).toBe("missing-remote-api-key");
+    expect(classifySyncStatusDenialReason(new ApiError(502, "Remote node authentication failed"))).toBe("auth-failed");
+    expect(classifySyncStatusDenialReason(new ApiError(504, "Remote node unreachable"))).toBe("unreachable");
+    expect(classifySyncStatusDenialReason("boom")).toBe("unknown");
+  });
+});