Add tests for Set iterator mutation and exhaustion behavior

RealColdFry · RealColdFry · commit 2bd60e8bcc81 · 2026-03-23T00:30:21.000Z
diff --git a/test/unit/builtins/set.spec.ts b/test/unit/builtins/set.spec.ts
@@ -195,17 +195,46 @@ describe.each(iterationMethods)("set.%s() preserves insertion order", iterationM
     });
 });
 
-test("set iterator persists after delete", () => {
-    util.testFunction`
-        const set1 = new Set<string | number>();
-        set1.add(42);
-        set1.add("forty two");
+describe.each(iterationMethods)("set.%s() handles mutation", iterationMethod => {
+    test("iterator persists after delete", () => {
+        util.testFunction`
+            const set1 = new Set<string | number>();
+            set1.add(42);
+            set1.add("forty two");
 
-        const iterator1 = set1.values();
-        set1.delete(42);
+            const iterator1 = set1.${iterationMethod}();
+            set1.delete(42);
 
-        return iterator1.next().value;
-    `.expectToMatchJsResult();
+            return iterator1.next().value;
+        `.expectToMatchJsResult();
+    });
+
+    test("iterator with delete and add between iterations", () => {
+        util.testFunction`
+            const set = new Set([1, 2, 3]);
+            const iter = set.${iterationMethod}();
+            iter.next(); // 1
+            set.delete(2);
+            set.add(4);
+            const results: IteratorResult<any>[] = [];
+            let r = iter.next();
+            while (!r.done) { results.push({ done: r.done, value: r.value }); r = iter.next(); }
+            return results;
+        `.expectToMatchJsResult();
+    });
+
+    test("iterator does not restart after exhaustion", () => {
+        util.testFunction`
+            const set = new Set([1, 2]);
+            const iter = set.${iterationMethod}();
+            const results: boolean[] = [];
+            results.push(iter.next().done!);
+            results.push(iter.next().done!);
+            results.push(iter.next().done!); // should be done
+            results.push(iter.next().done!); // should still be done, not restart
+            return results;
+        `.expectToMatchJsResult();
+    });
 });
 
 test("instanceof Set without creating set", () => {
