test: add initial pull delay and prototype pollution prevention tests

Refs : https://github.com/nodejs/node/blob/main/lib/internal/webstreams/readablestream.js#L522-L536 PR-URL: #54061 Reviewed-By: James M Snell <jasnell@gmail.com>

Author: sonsurim

test/parallel/test-whatwg-readablestream.js

@@ -1701,3 +1701,50 @@ class Source {
  assert.deepStrictEqual(value, new Uint8Array([1, 1, 1]));
  }));
 }
+
+// Initial Pull Delay
+{
+ const stream = new ReadableStream({
+ start(controller) {
+ controller.enqueue('data');
+ controller.close();
+ }
+ });
+
+ const iterator = stream.values();
+
+ let microtaskCompleted = false;
+ Promise.resolve().then(() => { microtaskCompleted = true; });
+
+ iterator.next().then(common.mustCall(({ done, value }) => {
+ assert.strictEqual(done, false);
+ assert.strictEqual(value, 'data');
+ assert.strictEqual(microtaskCompleted, true);
+ }));
+}
+
+// Avoiding Prototype Pollution
+{
+ const stream = new ReadableStream({
+ start(controller) {
+ controller.enqueue('data');
+ controller.close();
+ }
+ });
+
+ const iterator = stream.values();
+
+ // Modify Promise.prototype.then to simulate prototype pollution
+ const originalThen = Promise.prototype.then;
+ Promise.prototype.then = function(onFulfilled, onRejected) {
+ return originalThen.call(this, onFulfilled, onRejected);
+ };
+
+ iterator.next().then(common.mustCall(({ done, value }) => {
+ assert.strictEqual(done, false);
+ assert.strictEqual(value, 'data');
+
+ // Restore original then method
+ Promise.prototype.then = originalThen;
+ }));
+}