function run_test() { var sb = new Cu.Sandbox("http://www.example.com", { wantGlobalProperties: ["structuredClone"], }); sb.equal = equal; sb.testing = Cu.cloneInto({ xyz: 123 }, sb); Cu.evalInSandbox( ` equal(structuredClone("abc"), "abc"); var obj = { a: 1 }; obj.self = obj; var clone = structuredClone(obj); equal(clone.a, 1); equal(clone.self, clone); var ab = new ArrayBuffer(1); clone = structuredClone(ab, { transfer: [ab] }); equal(clone.byteLength, 1); equal(ab.byteLength, 0); clone = structuredClone(testing); equal(clone.xyz, 123); `, sb ); const clone = structuredClone({ b: 2 }); Assert.equal(clone.b, 2); }