Added test cases about Multiplex RPC component (#4172)

* 完善文档中 GRPC 包示例

* Added test cases about rpc-multiplex.

Co-authored-by: 李铭昕 <715557344@qq.com>

Author: sdfjklmin

tests/Cases/ChannelManagerTest.php

@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * This file is part of Hyperf.
+ *
+ * @link     https://www.hyperf.io
+ * @document https://hyperf.wiki
+ * @contact  group@hyperf.io
+ * @license  https://github.com/hyperf/hyperf/blob/master/LICENSE
+ */
+namespace HyperfTest\RpcMultiplex\Cases;
+
+use Hyperf\Utils\Coroutine;
+use Multiplex\ChannelManager;
+
+/**
+ * @internal
+ * @coversNothing
+ */
+class ChannelManagerTest extends AbstractTestCase
+{
+    public function testChannelManagerFlush()
+    {
+        $manager = new ChannelManager();
+        $chan = $manager->get(1, true);
+        $chan->push(true);
+        $chan2 = $manager->get(2, true);
+        $chan2->push(true);
+
+        Coroutine::create(function () use ($manager, $chan, $chan2) {
+            $chan->push(true);
+            $chan = $manager->get(3, true);
+            $chan->push(true);
+            $chan2->push(true);
+        });
+
+        $channels = $manager->getChannels();
+        foreach ($channels as $id => $channel) {
+            $manager->get($id + 3, true);
+            $manager->close($id);
+        }
+
+        $this->assertSame([4, 3, 5], array_keys($manager->getChannels()));
+    }
+}