1 files changed, 52 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Set/prototype/symmetricDifference/set-like-class-mutation.js b/js/src/tests/test262/built-ins/Set/prototype/symmetricDifference/set-like-class-mutation.js
new file mode 100644
index 0000000000..f75783bbed
--- /dev/null
+++ b/js/src/tests/test262/built-ins/Set/prototype/symmetricDifference/set-like-class-mutation.js
@@ -0,0 +1,52 @@
+// |reftest| skip -- set-methods is not supported
+// Copyright (C) 2023 Anthony Frehner and Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-set.prototype.symmetricdifference
+description: Set.prototype.symmetricDifference maintains values even when a custom Set-like class mutates the receiver
+features: [set-methods]
+includes: [compareArray.js]
+---*/
+
+const baseSet = new Set(["a", "b", "c", "d", "e"]);
+
+function mutatingIterator() {
+  let index = 0;
+  let values = ["x", "b", "c", "c"];
+  return {
+    next() {
+      if (index === 0) {
+        baseSet.delete("b");
+        baseSet.delete("c");
+        baseSet.add("b");
+        baseSet.add("d");
+      }
+      return {
+        done: index >= values.length,
+        value: values[index++],
+      };
+    },
+  };
+}
+
+const evilSetLike = {
+  size: 4,
+  get has() {
+    baseSet.add("q");
+    return function () {
+      throw new Test262Error("Set.prototype.symmetricDifference should not invoke .has on its argument");
+    };
+  },
+  keys() {
+    return mutatingIterator();
+  },
+};
+
+const combined = baseSet.symmetricDifference(evilSetLike);
+const expectedCombined = ["a", "c", "d", "e", "q", "x"];
+assert.compareArray([...combined], expectedCombined);
+
+const expectedNewBase = ["a", "d", "e", "q", "b"];
+assert.compareArray([...baseSet], expectedNewBase);
+
+reportCompare(0, 0);