From c5841edd273eb994fc58bb82a0b02eb03a69aac9 Mon Sep 17 00:00:00 2001
From: Vincent Driessen <me@nvie.com>
Date: Tue, 9 Jun 2026 12:26:38 +0200
Subject: [PATCH] Add property based test for new `isJsonEq` helper (#3500)

---
 .../__tests__/liveblocks-helpers.test.ts      | 24 ++++++++++++++++++-
 .../src/crdts/liveblocks-helpers.ts           |  2 +-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/packages/liveblocks-core/src/crdts/__tests__/liveblocks-helpers.test.ts b/packages/liveblocks-core/src/crdts/__tests__/liveblocks-helpers.test.ts
index 08492cb09a..da6f4225c9 100644
--- a/packages/liveblocks-core/src/crdts/__tests__/liveblocks-helpers.test.ts
+++ b/packages/liveblocks-core/src/crdts/__tests__/liveblocks-helpers.test.ts
@@ -1,3 +1,4 @@
+import fc from "fast-check";
 import { describe, expect, test } from "vitest";
 
 import {
@@ -7,10 +8,11 @@ import {
   SECOND_POSITION,
   THIRD_POSITION,
 } from "../../__tests__/_MockWebSocketServer.setup";
+import { stableStringify } from "../../lib/stringify";
 import { OpCode } from "../../protocol/Op";
 import type { NodeMap } from "../../protocol/StorageNode";
 import { CrdtType } from "../../protocol/StorageNode";
-import { getTreesDiffOperations } from "../liveblocks-helpers";
+import { getTreesDiffOperations, isJsonEq } from "../liveblocks-helpers";
 import { LiveList } from "../LiveList";
 import { LiveMap } from "../LiveMap";
 import { LiveObject } from "../LiveObject";
@@ -440,3 +442,23 @@ describe("toPlainLson", () => {
     expect(toPlainLson(mockLsonObject)).toEqual(plainLsonValue);
   });
 });
+
+describe("isJsonEq", () => {
+  test("[property] true iff the stable stringifications match", () => {
+    fc.assert(
+      fc.property(fc.jsonValue(), fc.jsonValue(), (j1, j2) => {
+        expect(isJsonEq(j1, j2)).toBe(
+          stableStringify(j1) === stableStringify(j2)
+        );
+      })
+    );
+  });
+
+  test("[property] reflexive: a value always equals (a clone of) itself", () => {
+    fc.assert(
+      fc.property(fc.jsonValue(), (j) => {
+        expect(isJsonEq(j, structuredClone(j))).toBe(true);
+      })
+    );
+  });
+});
diff --git a/packages/liveblocks-core/src/crdts/liveblocks-helpers.ts b/packages/liveblocks-core/src/crdts/liveblocks-helpers.ts
index a9a7280cf4..156048d6c0 100644
--- a/packages/liveblocks-core/src/crdts/liveblocks-helpers.ts
+++ b/packages/liveblocks-core/src/crdts/liveblocks-helpers.ts
@@ -201,7 +201,7 @@ export function dumpPool(pool: ManagedPool): string {
  * and nested arrays/objects are compared by traversal (key-by-key, so key order
  * is irrelevant).
  */
-function isJsonEq(a: Json | undefined, b: Json | undefined): boolean {
+export function isJsonEq(a: Json | undefined, b: Json | undefined): boolean {
   if (a === b) {
     return true;
   }