Bug 1753860 - Test using `structuredClone` in xpcshell. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D137959

js/xpconnect/tests/unit/test_structuredClone.js

@@ -1,25 +1,33 @@
 function run_test() {
-  var sb = new Cu.Sandbox('http://www.example.com',
-                          { wantGlobalProperties: ["structuredClone"] });
+  var sb = new Cu.Sandbox("http://www.example.com", {
+    wantGlobalProperties: ["structuredClone"],
+  });
 
   sb.equal = equal;
 
-  sb.testing =  Components.utils.cloneInto({xyz: 123}, sb);
-  Cu.evalInSandbox(`
+  sb.testing = Cu.cloneInto({ xyz: 123 }, sb);
+  Cu.evalInSandbox(
+    `
     equal(structuredClone("abc"), "abc");
 
-    var obj = {a: 1};
+    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]});
+    clone = structuredClone(ab, { transfer: [ab] });
     equal(clone.byteLength, 1);
     equal(ab.byteLength, 0);
 
     clone = structuredClone(testing);
     equal(clone.xyz, 123);
-  `, sb);
+    `,
+    sb
+  );
+
+  Cu.importGlobalProperties(["structuredClone"]);
+  const clone = structuredClone({ b: 2 });
+  Assert.equal(clone.b, 2);
 }