Add Chain test (#138)

tests/Middleware/ChainTest.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Yiisoft\Yii\Web\Tests\Middleware;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Yiisoft\Yii\Web\Middleware\Chain;
+use PHPUnit\Framework\TestCase;
+
+class ChainTest extends TestCase
+{
+    public function testProcess()
+    {
+        $request = $this->createMock(ServerRequestInterface::class);
+        $handler = $this->createMock(RequestHandlerInterface::class);
+
+        $middleware1 = $this->createMock(MiddlewareInterface::class);
+        $middleware1->expects($this->once())->method('process')->willReturnCallback(
+            function (ServerRequestInterface $request, RequestHandlerInterface $handler) {
+                return $handler->handle($request);
+            }
+        );
+
+        $middleware2 = $this->createMock(MiddlewareInterface::class);
+        $middleware2->expects($this->once())->method('process');
+
+        $chain = new Chain($middleware1, $middleware2);
+        $chain->process($request, $handler);
+    }
+}