Add test to confirm bad behavior of chaining

Author: joelwurtz

tests/PromiseTest.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Http\Adapter\React\Tests;
+
+use GuzzleHttp\Psr7\Response;
+use Http\Adapter\React\Promise;
+use Http\Adapter\React\ReactFactory;
+use PHPUnit\Framework\TestCase;
+use React\Promise\Deferred;
+
+class PromiseTest extends TestCase
+{
+    private $loop;
+
+    public function setUp()
+    {
+        $this->loop = ReactFactory::buildEventLoop();
+    }
+
+    public function testChain()
+    {
+        $deferred = new Deferred();
+        $promise = new Promise($deferred->promise());
+        $promise->setLoop($this->loop);
+        $response = new Response(200);
+
+        $lastPromise = $promise->then(function (Response $response) {
+            return $response->withStatus(300);
+        });
+
+        $deferred->resolve($response);
+        $updatedResponse = $lastPromise->wait();
+
+        self::assertEquals(200, $response->getStatusCode());
+        self::assertEquals(300, $updatedResponse->getStatusCode());
+    }
+}