docs(protocol): add test with cancelled request

Related: socketio/bun-engine@8f1ea3d

Author: darrachequesne

docs/engine.io-protocol/v4-test-suite/test-suite.js

@@ -332,6 +332,25 @@ describe("Engine.IO protocol", () => {
 
         expect(pollResponse.status).to.eql(400);
       });
+
+      it("closes the session upon cancelled polling request", async () => {
+        const sid = await initLongPollingSession();
+        const controller = new AbortController();
+
+        fetch(`${URL}/engine.io/?EIO=4&transport=polling&sid=${sid}`, {
+          signal: controller.signal,
+        }).catch(() => {});
+
+        await sleep(5);
+
+        controller.abort();
+
+        const pollResponse = await fetch(
+          `${URL}/engine.io/?EIO=4&transport=polling&sid=${sid}`,
+        );
+
+        expect(pollResponse.status).to.eql(400);
+      });
     });
 
     describe("WebSocket", () => {