From 40c6d6efa8459102463793be2e3377f8f0717953 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20L=C3=BCck?= <christian@clue.engineering>
Date: Tue, 15 Feb 2022 16:12:52 +0100
Subject: [PATCH 1/2] Automatically start new fiber for each request on PHP
 8.1+

---
 composer.json               |   3 +-
 examples/index.php          |  16 +++
 src/App.php                 |   7 +-
 src/FiberHandler.php        |  71 ++++++++++++
 tests/AppMiddlewareTest.php |  68 +++++++++---
 tests/AppTest.php           | 213 ++++++++++++++++++++++++++++++++----
 tests/FiberHandlerTest.php  | 193 ++++++++++++++++++++++++++++++++
 tests/acceptance.sh         |   4 +
 8 files changed, 539 insertions(+), 36 deletions(-)
 create mode 100644 src/FiberHandler.php
 create mode 100644 tests/FiberHandlerTest.php

diff --git a/composer.json b/composer.json
index c18e466..09420da 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,8 @@
         "react/promise": "^2.7"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.5 || ^7.5"
+        "phpunit/phpunit": "^9.5 || ^7.5",
+        "react/async": "^4@dev || ^3@dev"
     },
     "autoload": {
         "psr-4": {
diff --git a/examples/index.php b/examples/index.php
index 5f87b49..b16a3b8 100644
--- a/examples/index.php
+++ b/examples/index.php
@@ -24,6 +24,22 @@
     );
 });
 
+$app->get('/sleep/promise', function () {
+    return React\Promise\Timer\sleep(0.1)->then(function () {
+        return React\Http\Message\Response::plaintext("OK\n");
+    });
+});
+$app->get('/sleep/coroutine', function () {
+    yield React\Promise\Timer\sleep(0.1);
+    return React\Http\Message\Response::plaintext("OK\n");
+});
+if (PHP_VERSION_ID >= 80100 && function_exists('React\Async\async')) { // requires PHP 8.1+ with react/async 4+
+    $app->get('/sleep/fiber', function () {
+        React\Async\await(React\Promise\Timer\sleep(0.1));
+        return React\Http\Message\Response::plaintext("OK\n");
+    });
+}
+
 $app->get('/uri[/{path:.*}]', function (ServerRequestInterface $request) {
     return React\Http\Message\Response::plaintext(
         (string) $request->getUri() . "\n"
diff --git a/src/App.php b/src/App.php
index cf8ed4e..bb95ebc 100644
--- a/src/App.php
+++ b/src/App.php
@@ -52,7 +52,7 @@ public function __construct(...$middleware)
             }
         }
 
-        // new MiddlewareHandler([$accessLogHandler, $errorHandler, ...$middleware, $routeHandler])
+        // new MiddlewareHandler([$fiberHandler, $accessLogHandler, $errorHandler, ...$middleware, $routeHandler])
         \array_unshift($middleware, $errorHandler);
 
         // only log for built-in webserver and PHP development webserver by default, others have their own access log
@@ -60,6 +60,11 @@ public function __construct(...$middleware)
             \array_unshift($middleware, new AccessLogHandler());
         }
 
+        // automatically start new fiber for each request on PHP 8.1+
+        if (\PHP_VERSION_ID >= 80100) {
+            \array_unshift($middleware, new FiberHandler()); // @codeCoverageIgnore
+        }
+
         $this->router = new RouteHandler($container);
         $middleware[] = $this->router;
         $this->handler = new MiddlewareHandler($middleware);
diff --git a/src/FiberHandler.php b/src/FiberHandler.php
new file mode 100644
index 0000000..38d7ab8
--- /dev/null
+++ b/src/FiberHandler.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace FrameworkX;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use React\Promise\Deferred;
+use React\Promise\Promise;
+use React\Promise\PromiseInterface;
+
+/**
+ * [Internal] Fibers middleware handler to ensure each request is processed in a separate `Fiber`
+ *
+ * The `Fiber` class has been added in PHP 8.1+, so this middleware is only used
+ * on PHP 8.1+. On supported PHP versions, this middleware is automatically
+ * added to the list of middleware handlers, so there's no need to reference
+ * this class in application code.
+ *
+ * @internal
+ * @link https://framework-x.org/docs/async/fibers/
+ */
+class FiberHandler
+{
+    /**
+     * @return PromiseInterface<ResponseInterface,void>
+     *     Returns a promise that is fulfilled with a `ResponseInterface` on
+     *     success. This method never throws or resolves a rejected promise.
+     *     If the request can not be routed or the handler fails, it will be
+     *     turned into a valid error response before returning.
+     * @throws void
+     */
+    public function __invoke(ServerRequestInterface $request, callable $next): PromiseInterface
+    {
+        return new Promise(function ($resolve) use ($next, $request) {
+            $fiber = new \Fiber(function () use ($resolve, $next, $request) {
+                $response = $next($request);
+                if ($response instanceof \Generator) {
+                    $response = $this->coroutine($response);
+                }
+
+                $resolve($response);
+            });
+            $fiber->start();
+        });
+    }
+
+    private function coroutine(\Generator $generator): PromiseInterface
+    {
+        $next = null;
+        $deferred = new Deferred();
+        $next = function () use ($generator, &$next, $deferred) {
+            if (!$generator->valid()) {
+                $deferred->resolve($generator->getReturn());
+                return;
+            }
+
+            $promise = $generator->current();
+            $promise->then(function ($value) use ($generator, $next) {
+                $generator->send($value);
+                $next();
+            }, function ($reason) use ($generator, $next) {
+                $generator->throw($reason);
+                $next();
+            });
+        };
+
+        $next();
+
+        return $deferred->promise();
+    }
+}
diff --git a/tests/AppMiddlewareTest.php b/tests/AppMiddlewareTest.php
index d891851..cc6f804 100644
--- a/tests/AppMiddlewareTest.php
+++ b/tests/AppMiddlewareTest.php
@@ -2,7 +2,9 @@
 
 namespace FrameworkX\Tests;
 
+use FrameworkX\AccessLogHandler;
 use FrameworkX\App;
+use FrameworkX\FiberHandler;
 use FrameworkX\RouteHandler;
 use PHPUnit\Framework\TestCase;
 use Psr\Http\Message\ResponseInterface;
@@ -169,7 +171,7 @@ public function testMapMethodWithMiddlewareAddsGivenMethodsOnRouter()
 
     public function testMiddlewareCallsNextReturnsResponseFromRouter()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             return $next($request);
@@ -203,7 +205,7 @@ public function testMiddlewareCallsNextReturnsResponseFromRouter()
 
     public function testMiddlewareCallsNextWithModifiedRequestReturnsResponseFromRouter()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             return $next($request->withAttribute('name', 'Alice'));
@@ -237,7 +239,7 @@ public function testMiddlewareCallsNextWithModifiedRequestReturnsResponseFromRou
 
     public function testMiddlewareCallsNextReturnsResponseModifiedInMiddlewareFromRouter()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             $response = $next($request);
@@ -364,7 +366,7 @@ public function testMiddlewareCallsNextReturnsCoroutineResponseModifiedInMiddlew
 
     public function testMiddlewareCallsNextWhichThrowsExceptionReturnsInternalServerErrorResponse()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             return $next($request);
@@ -395,7 +397,7 @@ public function testMiddlewareCallsNextWhichThrowsExceptionReturnsInternalServer
 
     public function testMiddlewareWhichThrowsExceptionReturnsInternalServerErrorResponse()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $line = __LINE__ + 2;
         $middleware = function (ServerRequestInterface $request, callable $next) {
@@ -424,7 +426,7 @@ public function testMiddlewareWhichThrowsExceptionReturnsInternalServerErrorResp
 
     public function testGlobalMiddlewareCallsNextReturnsResponseFromController()
     {
-        $app = $this->createAppWithoutLogger(function (ServerRequestInterface $request, callable $next) {
+        $app = $this->createAppWithoutFibersOrLogger(function (ServerRequestInterface $request, callable $next) {
             return $next($request);
         });
 
@@ -461,7 +463,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
             }
         };
 
-        $app = $this->createAppWithoutLogger($middleware);
+        $app = $this->createAppWithoutFibersOrLogger($middleware);
 
         $app->get('/', function () {
             return new Response(
@@ -496,7 +498,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
             }
         };
 
-        $app = $this->createAppWithoutLogger(get_class($middleware));
+        $app = $this->createAppWithoutFibersOrLogger(get_class($middleware));
 
         $app->get('/', function () {
             return new Response(
@@ -532,7 +534,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
             }
         };
 
-        $app = $this->createAppWithoutLogger(get_class($middleware));
+        $app = $this->createAppWithoutFibersOrLogger(get_class($middleware));
 
         $app->get('/', get_class($middleware), function (ServerRequestInterface $request) {
             return new Response(
@@ -560,7 +562,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
 
     public function testGlobalMiddlewareCallsNextWithModifiedRequestWillBeUsedForRouting()
     {
-        $app = $this->createAppWithoutLogger(function (ServerRequestInterface $request, callable $next) {
+        $app = $this->createAppWithoutFibersOrLogger(function (ServerRequestInterface $request, callable $next) {
             return $next($request->withUri($request->getUri()->withPath('/users')));
         });
 
@@ -590,7 +592,7 @@ public function testGlobalMiddlewareCallsNextWithModifiedRequestWillBeUsedForRou
 
     public function testGlobalMiddlewareCallsNextReturnsModifiedResponseWhenModifyingResponseFromRouter()
     {
-        $app = $this->createAppWithoutLogger(function (ServerRequestInterface $request, callable $next) {
+        $app = $this->createAppWithoutFibersOrLogger(function (ServerRequestInterface $request, callable $next) {
             $response = $next($request);
             assert($response instanceof ResponseInterface);
 
@@ -621,7 +623,7 @@ public function testGlobalMiddlewareCallsNextReturnsModifiedResponseWhenModifyin
 
     public function testGlobalMiddlewareReturnsResponseWithoutCallingNextReturnsResponseWithoutCallingRouter()
     {
-        $app = $this->createAppWithoutLogger(function () {
+        $app = $this->createAppWithoutFibersOrLogger(function () {
             return new Response(
                 200,
                 [
@@ -788,8 +790,46 @@ private function createAppWithoutLogger(...$middleware): App
         $ref->setAccessible(true);
         $handlers = $ref->getValue($middleware);
 
-        unset($handlers[0]);
-        $ref->setValue($middleware, array_values($handlers));
+        if (PHP_VERSION_ID >= 80100) {
+            $first = array_shift($handlers);
+            $this->assertInstanceOf(FiberHandler::class, $first);
+
+            $next = array_shift($handlers);
+            $this->assertInstanceOf(AccessLogHandler::class, $next);
+
+            array_unshift($handlers, $next, $first);
+        }
+
+        $first = array_shift($handlers);
+        $this->assertInstanceOf(AccessLogHandler::class, $first);
+
+        $ref->setValue($middleware, $handlers);
+
+        return $app;
+    }
+
+    /** @param callable|class-string ...$middleware */
+    private function createAppWithoutFibersOrLogger(...$middleware): App
+    {
+        $app = new App(...$middleware);
+
+        $ref = new \ReflectionProperty($app, 'handler');
+        $ref->setAccessible(true);
+        $middleware = $ref->getValue($app);
+
+        $ref = new \ReflectionProperty($middleware, 'handlers');
+        $ref->setAccessible(true);
+        $handlers = $ref->getValue($middleware);
+
+        if (PHP_VERSION_ID >= 80100) {
+            $first = array_shift($handlers);
+            $this->assertInstanceOf(FiberHandler::class, $first);
+        }
+
+        $first = array_shift($handlers);
+        $this->assertInstanceOf(AccessLogHandler::class, $first);
+
+        $ref->setValue($middleware, $handlers);
 
         return $app;
     }
diff --git a/tests/AppTest.php b/tests/AppTest.php
index 7733ff5..8261cdf 100644
--- a/tests/AppTest.php
+++ b/tests/AppTest.php
@@ -6,6 +6,7 @@
 use FrameworkX\App;
 use FrameworkX\Container;
 use FrameworkX\ErrorHandler;
+use FrameworkX\FiberHandler;
 use FrameworkX\MiddlewareHandler;
 use FrameworkX\RouteHandler;
 use FrameworkX\SapiHandler;
@@ -30,6 +31,7 @@
 use React\Promise\PromiseInterface;
 use ReflectionMethod;
 use ReflectionProperty;
+use function React\Async\await;
 use function React\Promise\reject;
 use function React\Promise\resolve;
 
@@ -72,6 +74,11 @@ public function testConstructWithMiddlewareAssignsGivenMiddleware()
         $ref->setAccessible(true);
         $handlers = $ref->getValue($handler);
 
+        if (PHP_VERSION_ID >= 80100) {
+            $first = array_shift($handlers);
+            $this->assertInstanceOf(FiberHandler::class, $first);
+        }
+
         $this->assertCount(4, $handlers);
         $this->assertInstanceOf(AccessLogHandler::class, $handlers[0]);
         $this->assertInstanceOf(ErrorHandler::class, $handlers[1]);
@@ -93,6 +100,11 @@ public function testConstructWithContainerAssignsContainerForRouteHandlerOnly()
         $ref->setAccessible(true);
         $handlers = $ref->getValue($handler);
 
+        if (PHP_VERSION_ID >= 80100) {
+            $first = array_shift($handlers);
+            $this->assertInstanceOf(FiberHandler::class, $first);
+        }
+
         $this->assertCount(3, $handlers);
         $this->assertInstanceOf(AccessLogHandler::class, $handlers[0]);
         $this->assertInstanceOf(ErrorHandler::class, $handlers[1]);
@@ -122,6 +134,11 @@ public function testConstructWithContainerAndMiddlewareClassNameAssignsCallableF
         $ref->setAccessible(true);
         $handlers = $ref->getValue($handler);
 
+        if (PHP_VERSION_ID >= 80100) {
+            $first = array_shift($handlers);
+            $this->assertInstanceOf(FiberHandler::class, $first);
+        }
+
         $this->assertCount(4, $handlers);
         $this->assertInstanceOf(AccessLogHandler::class, $handlers[0]);
         $this->assertInstanceOf(ErrorHandler::class, $handlers[1]);
@@ -225,7 +242,7 @@ public function testRunAppWithBusyPortThrows()
 
     public function testRunOnceWillCreateRequestFromSapiThenRouteRequestAndThenSendResponseFromHandler()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $response = new Response();
         $app->get('/', function () use ($response) {
@@ -251,7 +268,7 @@ public function testRunOnceWillCreateRequestFromSapiThenRouteRequestAndThenSendR
 
     public function testRunOnceWillCreateRequestFromSapiThenRouteRequestAndThenSendResponseFromDeferredHandler()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $response = new Response();
         $app->get('/', function () use ($response) {
@@ -467,7 +484,7 @@ public function testRedirectMethodWithCustomRedirectCodeAddsAnyRouteOnRouterWhic
 
     public function testHandleRequestWithProxyRequestReturnsResponseWithMessageThatProxyRequestsAreNotAllowed()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $request = new ServerRequest('GET', 'http://google.com/');
         $request = $request->withRequestTarget('http://google.com/');
@@ -489,7 +506,7 @@ public function testHandleRequestWithProxyRequestReturnsResponseWithMessageThatP
 
     public function testHandleRequestWithUnknownRouteReturnsResponseWithFileNotFoundMessage()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $request = new ServerRequest('GET', 'http://localhost/invalid');
 
@@ -510,7 +527,7 @@ public function testHandleRequestWithUnknownRouteReturnsResponseWithFileNotFound
 
     public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithSingleMethodNotAllowedMessage()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->get('/users', function () { });
 
@@ -534,7 +551,7 @@ public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithSing
 
     public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithMultipleMethodNotAllowedMessage()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->get('/users', function () { });
         $app->head('/users', function () { });
@@ -560,7 +577,7 @@ public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithMult
 
     public function testHandleRequestWithMatchingRouteReturnsResponseFromMatchingRouteHandler()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->get('/users', function () {
             return new Response(
@@ -588,7 +605,7 @@ public function testHandleRequestWithMatchingRouteReturnsResponseFromMatchingRou
 
     public function testHandleRequestWithOptionsAsteriskRequestReturnsResponseFromMatchingEmptyRouteHandler()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->options('', function () {
             return new Response(
@@ -681,7 +698,7 @@ public function testHandleRequestWithMatchingRouteReturnsPendingPromiseWhenHandl
 
     public function testHandleRequestWithMatchingRouteReturnsResponseWhenHandlerReturnsCoroutineWhichReturnsResponseWithoutYielding()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->get('/users', function () {
             if (false) {
@@ -820,10 +837,90 @@ public function testHandleRequestWithMatchingRouteReturnsPendingPromiseWhenHandl
         $this->assertFalse($resolved);
     }
 
-    public function testHandleRequestWithMatchingRouteAndRouteVariablesReturnsResponseFromHandlerWithRouteVariablesAssignedAsRequestAttributes()
+    public function testHandleRequestWithMatchingRouteReturnsPromiseResolvingWithResponseWhenHandlerReturnsResponse()
+    {
+        if (PHP_VERSION_ID < 80100) {
+            $this->markTestSkipped('Requires PHP 8.1+');
+        }
+
+        $app = $this->createAppWithoutLogger();
+
+        $app->get('/users', function () {
+            return new Response(
+                200,
+                [
+                    'Content-Type' => 'text/html'
+                ],
+                "OK\n"
+            );
+        });
+
+        $request = new ServerRequest('GET', 'http://localhost/users');
+
+        // $promise = $app->handleRequest($request);
+        $ref = new ReflectionMethod($app, 'handleRequest');
+        $ref->setAccessible(true);
+        $promise = $ref->invoke($app, $request);
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $response = null;
+        $promise->then(function ($value) use (&$response) {
+            $response = $value;
+        });
+
+        /** @var ResponseInterface $response */
+        $this->assertInstanceOf(ResponseInterface::class, $response);
+        $this->assertEquals(200, $response->getStatusCode());
+        $this->assertEquals('text/html', $response->getHeaderLine('Content-Type'));
+        $this->assertEquals("OK\n", (string) $response->getBody());
+    }
+
+    public function testHandleRequestWithMatchingRouteReturnsPromiseResolvingWithResponseWhenHandlerReturnsResponseAfterAwaitingPromiseResolvingWithResponse()
     {
+        if (PHP_VERSION_ID < 80100 || !function_exists('React\Async\async')) {
+            $this->markTestSkipped('Requires PHP 8.1+ with react/async 4+');
+        }
+
         $app = $this->createAppWithoutLogger();
 
+        $app->get('/users', function () {
+            return await(resolve(new Response(
+                200,
+                [
+                    'Content-Type' => 'text/html'
+                ],
+                "OK\n"
+            )));
+        });
+
+        $request = new ServerRequest('GET', 'http://localhost/users');
+
+        // $promise = $app->handleRequest($request);
+        $ref = new ReflectionMethod($app, 'handleRequest');
+        $ref->setAccessible(true);
+        $promise = $ref->invoke($app, $request);
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $response = null;
+        $promise->then(function ($value) use (&$response) {
+            $response = $value;
+        });
+
+        /** @var ResponseInterface $response */
+        $this->assertInstanceOf(ResponseInterface::class, $response);
+        $this->assertEquals(200, $response->getStatusCode());
+        $this->assertEquals('text/html', $response->getHeaderLine('Content-Type'));
+        $this->assertEquals("OK\n", (string) $response->getBody());
+    }
+
+    public function testHandleRequestWithMatchingRouteAndRouteVariablesReturnsResponseFromHandlerWithRouteVariablesAssignedAsRequestAttributes()
+    {
+        $app = $this->createAppWithoutFibersOrLogger();
+
         $app->get('/users/{name}', function (ServerRequestInterface $request) {
             $name = $request->getAttribute('name');
 
@@ -852,7 +949,7 @@ public function testHandleRequestWithMatchingRouteAndRouteVariablesReturnsRespon
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerThrowsException()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $line = __LINE__ + 2;
         $app->get('/users', function () {
@@ -983,7 +1080,7 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWit
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerReturnsCoroutineWhichThrowsExceptionWithoutYielding()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $line = __LINE__ + 5;
         $app->get('/users', function () {
@@ -1047,6 +1144,45 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWit
         $this->assertStringContainsString("<p>Expected request handler to return <code>Psr\Http\Message\ResponseInterface</code> but got uncaught <code>RuntimeException</code> with message <code>Foo</code> in <code title=\"See " . __FILE__ . " line $line\">AppTest.php:$line</code>.</p>\n", (string) $response->getBody());
     }
 
+    public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWithInternalServerErrorResponseWhenHandlerThrowsAfterAwaitingPromiseRejectingWithException()
+    {
+        if (PHP_VERSION_ID < 80100 || !function_exists('React\Async\async')) {
+            $this->markTestSkipped('Requires PHP 8.1+ with react/async 4+');
+        }
+
+        $app = $this->createAppWithoutLogger();
+
+        $line = __LINE__ + 2;
+        $app->get('/users', function () {
+            return await(reject(new \RuntimeException('Foo')));
+        });
+
+        $request = new ServerRequest('GET', 'http://localhost/users');
+
+        // $promise = $app->handleRequest($request);
+        $ref = new ReflectionMethod($app, 'handleRequest');
+        $ref->setAccessible(true);
+        $promise = $ref->invoke($app, $request);
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $response = null;
+        $promise->then(function ($value) use (&$response) {
+            $response = $value;
+        });
+
+        /** @var ResponseInterface $response */
+        $this->assertInstanceOf(ResponseInterface::class, $response);
+        $this->assertEquals(500, $response->getStatusCode());
+        $this->assertEquals('text/html; charset=utf-8', $response->getHeaderLine('Content-Type'));
+        $this->assertStringMatchesFormat("<!DOCTYPE html>\n<html>%a</html>\n", (string) $response->getBody());
+
+        $this->assertStringContainsString("<title>Error 500: Internal Server Error</title>\n", (string) $response->getBody());
+        $this->assertStringContainsString("<p>The requested page failed to load, please try again later.</p>\n", (string) $response->getBody());
+        $this->assertStringContainsString("<p>Expected request handler to return <code>Psr\Http\Message\ResponseInterface</code> but got uncaught <code>RuntimeException</code> with message <code>Foo</code> in <code title=\"See " . __FILE__ . " line $line\">AppTest.php:$line</code>.</p>\n", (string) $response->getBody());
+    }
+
     public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWithInternalServerErrorResponseWhenHandlerReturnsCoroutineWhichReturnsNull()
     {
         $app = $this->createAppWithoutLogger();
@@ -1084,7 +1220,7 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWit
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerReturnsCoroutineWhichYieldsNullImmediately()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $line = __LINE__ + 3;
         $app->get('/users', function () {
@@ -1111,7 +1247,7 @@ public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResp
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerReturnsWrongValue()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->get('/users', function () {
             return null;
@@ -1137,7 +1273,7 @@ public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResp
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassDoesNotExist()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->get('/users', 'UnknownClass');
 
@@ -1228,7 +1364,7 @@ public function provideInvalidClasses()
      */
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassIsInvalid(string $class, string $error)
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $app->get('/users', $class);
 
@@ -1252,7 +1388,7 @@ public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResp
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassRequiresUnexpectedCallableParameter()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $line = __LINE__ + 2;
         $controller = new class {
@@ -1281,7 +1417,7 @@ public function __invoke(int $value) { }
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassHasNoInvokeMethod()
     {
-        $app = $this->createAppWithoutLogger();
+        $app = $this->createAppWithoutFibersOrLogger();
 
         $controller = new class { };
 
@@ -1386,8 +1522,45 @@ private function createAppWithoutLogger(): App
         $ref->setAccessible(true);
         $handlers = $ref->getValue($middleware);
 
-        unset($handlers[0]);
-        $ref->setValue($middleware, array_values($handlers));
+        if (PHP_VERSION_ID >= 80100) {
+            $first = array_shift($handlers);
+            $this->assertInstanceOf(FiberHandler::class, $first);
+
+            $next = array_shift($handlers);
+            $this->assertInstanceOf(AccessLogHandler::class, $next);
+
+            array_unshift($handlers, $next, $first);
+        }
+
+        $first = array_shift($handlers);
+        $this->assertInstanceOf(AccessLogHandler::class, $first);
+
+        $ref->setValue($middleware, $handlers);
+
+        return $app;
+    }
+
+    private function createAppWithoutFibersOrLogger(): App
+    {
+        $app = new App();
+
+        $ref = new \ReflectionProperty($app, 'handler');
+        $ref->setAccessible(true);
+        $middleware = $ref->getValue($app);
+
+        $ref = new \ReflectionProperty($middleware, 'handlers');
+        $ref->setAccessible(true);
+        $handlers = $ref->getValue($middleware);
+
+        if (PHP_VERSION_ID >= 80100) {
+            $first = array_shift($handlers);
+            $this->assertInstanceOf(FiberHandler::class, $first);
+        }
+
+        $first = array_shift($handlers);
+        $this->assertInstanceOf(AccessLogHandler::class, $first);
+
+        $ref->setValue($middleware, $handlers);
 
         return $app;
     }
diff --git a/tests/FiberHandlerTest.php b/tests/FiberHandlerTest.php
new file mode 100644
index 0000000..8525c30
--- /dev/null
+++ b/tests/FiberHandlerTest.php
@@ -0,0 +1,193 @@
+<?php
+
+namespace Framework\Tests;
+
+use FrameworkX\FiberHandler;
+use PHPUnit\Framework\TestCase;
+use React\EventLoop\Loop;
+use React\Http\Message\Response;
+use React\Http\Message\ServerRequest;
+use React\Promise\Deferred;
+use React\Promise\Promise;
+use React\Promise\PromiseInterface;
+use function React\Async\await;
+use function React\Promise\reject;
+use function React\Promise\resolve;
+
+class FiberHandlerTest extends TestCase
+{
+    public function setUp(): void
+    {
+        if (PHP_VERSION_ID < 80100 || !function_exists('React\Async\async')) {
+            $this->markTestSkipped('Requires PHP 8.1+ with react/async 4+');
+        }
+    }
+
+    public function testInvokeWithHandlerReturningResponseReturnsPromiseResolvingWithSameResponse()
+    {
+        $handler = new FiberHandler();
+
+        $request = new ServerRequest('GET', 'http://example.com/');
+        $response = new Response();
+
+        $promise = $handler($request, function () use ($response) { return $response; });
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $ret = null;
+        $promise->then(function ($value) use (&$ret) {
+            $ret = $value;
+        });
+
+        $this->assertSame($response, $ret);
+    }
+
+    public function testInvokeWithHandlerReturningPromiseResolvingWithResponseReturnsPromiseResolvingWithSameResponse()
+    {
+        $handler = new FiberHandler();
+
+        $request = new ServerRequest('GET', 'http://example.com/');
+        $response = new Response();
+
+        $promise = $handler($request, function () use ($response) { return resolve($response); });
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $ret = null;
+        $promise->then(function ($value) use (&$ret) {
+            $ret = $value;
+        });
+
+        $this->assertSame($response, $ret);
+    }
+
+    public function testInvokeWithHandlerReturningGeneratorReturningResponseReturnsPromiseResolvingWithSameResponse()
+    {
+        $handler = new FiberHandler();
+
+        $request = new ServerRequest('GET', 'http://example.com/');
+        $response = new Response();
+
+        $promise = $handler($request, function () use ($response) {
+            if (false) {
+                yield;
+            }
+            return $response;
+        });
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $ret = null;
+        $promise->then(function ($value) use (&$ret) {
+            $ret = $value;
+        });
+
+        $this->assertSame($response, $ret);
+    }
+
+    public function testInvokeWithHandlerReturningGeneratorReturningResponseAfterYieldingResolvedPromiseReturnsPromiseResolvingWithSameResponse()
+    {
+        $handler = new FiberHandler();
+
+        $request = new ServerRequest('GET', 'http://example.com/');
+        $response = new Response();
+
+        $promise = $handler($request, function () use ($response) {
+            return yield resolve($response);
+        });
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $ret = null;
+        $promise->then(function ($value) use (&$ret) {
+            $ret = $value;
+        });
+
+        $this->assertSame($response, $ret);
+    }
+
+    public function testInvokeWithHandlerReturningGeneratorReturningResponseAfterYieldingRejectedPromiseReturnsPromiseResolvingWithSameResponse()
+    {
+        $handler = new FiberHandler();
+
+        $request = new ServerRequest('GET', 'http://example.com/');
+        $response = new Response();
+
+        $promise = $handler($request, function () use ($response) {
+            try {
+                yield reject(new \RuntimeException('Foo'));
+            } catch (\RuntimeException $e) {
+                return $response;
+            }
+        });
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $ret = null;
+        $promise->then(function ($value) use (&$ret) {
+            $ret = $value;
+        });
+
+        $this->assertSame($response, $ret);
+    }
+
+    public function testInvokeWithHandlerReturningResponseAfterAwaitingResolvedPromiseReturnsPromiseResolvingWithSameResponse()
+    {
+        $handler = new FiberHandler();
+
+        $request = new ServerRequest('GET', 'http://example.com/');
+        $response = new Response();
+
+        $promise = $handler($request, function () use ($response) {
+            return await(resolve($response));
+        });
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $ret = null;
+        $promise->then(function ($value) use (&$ret) {
+            $ret = $value;
+        });
+
+        $this->assertSame($response, $ret);
+    }
+
+    public function testInvokeWithHandlerReturningResponseAfterAwaitingPendingPromiseReturnsPromiseResolvingWithSameResponse()
+    {
+        $handler = new FiberHandler();
+
+        $request = new ServerRequest('GET', 'http://example.com/');
+        $response = new Response();
+
+        $deferred = new Deferred();
+
+        $promise = $handler($request, function () use ($deferred) {
+            return await($deferred->promise());
+        });
+
+        /** @var PromiseInterface $promise */
+        $this->assertInstanceOf(PromiseInterface::class, $promise);
+
+        $ret = null;
+        $promise->then(function ($value) use (&$ret) {
+            $ret = $value;
+        });
+
+        $this->assertNull($ret);
+
+        $deferred->resolve($response);
+
+        // await next tick: https://github.com/reactphp/async/issues/27
+        await(new Promise(function ($resolve) {
+            Loop::futureTick($resolve);
+        }));
+
+        $this->assertSame($response, $ret);
+    }
+}
diff --git a/tests/acceptance.sh b/tests/acceptance.sh
index 5ecb1fd..dec09b7 100755
--- a/tests/acceptance.sh
+++ b/tests/acceptance.sh
@@ -26,6 +26,10 @@ out=$(curl -v $base/ 2>&1 -X POST); match "HTTP/.* 405"
 out=$(curl -v $base/error 2>&1);        match "HTTP/.* 500" && match -iP "Content-Type: text/html; charset=utf-8[\r\n]" && match "<code>Unable to load error</code>"
 out=$(curl -v $base/error/null 2>&1);   match "HTTP/.* 500" && match -iP "Content-Type: text/html; charset=utf-8[\r\n]"
 
+out=$(curl -v $base/sleep/promise 2>&1);    match "HTTP/.* 200" && match -iP "Content-Type: text/plain; charset=utf-8[\r\n]"
+out=$(curl -v $base/sleep/coroutine 2>&1);  match "HTTP/.* 200" && match -iP "Content-Type: text/plain; charset=utf-8[\r\n]"
+out=$(curl -v $base/sleep/fiber 2>&1);      skipif "HTTP/.* 404" && match "HTTP/.* 200" && match -iP "Content-Type: text/plain; charset=utf-8[\r\n]" # skip PHP < 8.1
+
 out=$(curl -v $base/uri 2>&1);                          match "HTTP/.* 200" && match "$base/uri"
 out=$(curl -v $base/uri/ 2>&1);                         match "HTTP/.* 200" && match "$base/uri/"
 out=$(curl -v $base/uri/foo 2>&1);                      match "HTTP/.* 200" && match "$base/uri/foo"

From f61d0e3e3579da092b8cfda88022c082e9d14d29 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20L=C3=BCck?= <christian@clue.engineering>
Date: Tue, 15 Feb 2022 20:21:05 +0100
Subject: [PATCH 2/2] Improve `FiberHandler` to only wrap in promise when using
 `await()`

---
 src/FiberHandler.php        |  63 +++++++--------
 tests/AppMiddlewareTest.php |  50 +++---------
 tests/AppTest.php           | 148 +++++++++++++-----------------------
 tests/FiberHandlerTest.php  |  68 +++++------------
 4 files changed, 113 insertions(+), 216 deletions(-)

diff --git a/src/FiberHandler.php b/src/FiberHandler.php
index 38d7ab8..bc432dd 100644
--- a/src/FiberHandler.php
+++ b/src/FiberHandler.php
@@ -5,7 +5,6 @@
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use React\Promise\Deferred;
-use React\Promise\Promise;
 use React\Promise\PromiseInterface;
 
 /**
@@ -22,50 +21,40 @@
 class FiberHandler
 {
     /**
-     * @return PromiseInterface<ResponseInterface,void>
-     *     Returns a promise that is fulfilled with a `ResponseInterface` on
-     *     success. This method never throws or resolves a rejected promise.
-     *     If the request can not be routed or the handler fails, it will be
-     *     turned into a valid error response before returning.
+     * @return ResponseInterface|PromiseInterface<ResponseInterface,void>|\Generator
+     *     Returns a `ResponseInterface` from the next request handler in the
+     *     chain. If the next request handler returns immediately, this method
+     *     will return immediately. If the next request handler suspends the
+     *     fiber (see `await()`), this method will return a `PromiseInterface`
+     *     that is fulfilled with a `ResponseInterface` when the fiber is
+     *     terminated successfully. If the next request handler returns a
+     *     promise, this method will return a promise that follows its
+     *     resolution. If the next request handler returns a Generator-based
+     *     coroutine, this method returns a `Generator`. This method never
+     *     throws or resolves a rejected promise. If the handler fails, it will
+     *     be turned into a valid error response before returning.
      * @throws void
      */
-    public function __invoke(ServerRequestInterface $request, callable $next): PromiseInterface
+    public function __invoke(ServerRequestInterface $request, callable $next): mixed
     {
-        return new Promise(function ($resolve) use ($next, $request) {
-            $fiber = new \Fiber(function () use ($resolve, $next, $request) {
-                $response = $next($request);
-                if ($response instanceof \Generator) {
-                    $response = $this->coroutine($response);
-                }
+        $deferred = null;
+        $fiber = new \Fiber(function () use ($request, $next, &$deferred) {
+            $response = $next($request);
+            assert($response instanceof ResponseInterface || $response instanceof PromiseInterface || $response instanceof \Generator);
 
-                $resolve($response);
-            });
-            $fiber->start();
-        });
-    }
-
-    private function coroutine(\Generator $generator): PromiseInterface
-    {
-        $next = null;
-        $deferred = new Deferred();
-        $next = function () use ($generator, &$next, $deferred) {
-            if (!$generator->valid()) {
-                $deferred->resolve($generator->getReturn());
-                return;
+            if ($deferred !== null) {
+                $deferred->resolve($response);
             }
 
-            $promise = $generator->current();
-            $promise->then(function ($value) use ($generator, $next) {
-                $generator->send($value);
-                $next();
-            }, function ($reason) use ($generator, $next) {
-                $generator->throw($reason);
-                $next();
-            });
-        };
+            return $response;
+        });
 
-        $next();
+        $fiber->start();
+        if ($fiber->isTerminated()) {
+            return $fiber->getReturn();
+        }
 
+        $deferred = new Deferred();
         return $deferred->promise();
     }
 }
diff --git a/tests/AppMiddlewareTest.php b/tests/AppMiddlewareTest.php
index cc6f804..35fec4d 100644
--- a/tests/AppMiddlewareTest.php
+++ b/tests/AppMiddlewareTest.php
@@ -171,7 +171,7 @@ public function testMapMethodWithMiddlewareAddsGivenMethodsOnRouter()
 
     public function testMiddlewareCallsNextReturnsResponseFromRouter()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             return $next($request);
@@ -205,7 +205,7 @@ public function testMiddlewareCallsNextReturnsResponseFromRouter()
 
     public function testMiddlewareCallsNextWithModifiedRequestReturnsResponseFromRouter()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             return $next($request->withAttribute('name', 'Alice'));
@@ -239,7 +239,7 @@ public function testMiddlewareCallsNextWithModifiedRequestReturnsResponseFromRou
 
     public function testMiddlewareCallsNextReturnsResponseModifiedInMiddlewareFromRouter()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             $response = $next($request);
@@ -366,7 +366,7 @@ public function testMiddlewareCallsNextReturnsCoroutineResponseModifiedInMiddlew
 
     public function testMiddlewareCallsNextWhichThrowsExceptionReturnsInternalServerErrorResponse()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $middleware = function (ServerRequestInterface $request, callable $next) {
             return $next($request);
@@ -397,7 +397,7 @@ public function testMiddlewareCallsNextWhichThrowsExceptionReturnsInternalServer
 
     public function testMiddlewareWhichThrowsExceptionReturnsInternalServerErrorResponse()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $line = __LINE__ + 2;
         $middleware = function (ServerRequestInterface $request, callable $next) {
@@ -426,7 +426,7 @@ public function testMiddlewareWhichThrowsExceptionReturnsInternalServerErrorResp
 
     public function testGlobalMiddlewareCallsNextReturnsResponseFromController()
     {
-        $app = $this->createAppWithoutFibersOrLogger(function (ServerRequestInterface $request, callable $next) {
+        $app = $this->createAppWithoutLogger(function (ServerRequestInterface $request, callable $next) {
             return $next($request);
         });
 
@@ -463,7 +463,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
             }
         };
 
-        $app = $this->createAppWithoutFibersOrLogger($middleware);
+        $app = $this->createAppWithoutLogger($middleware);
 
         $app->get('/', function () {
             return new Response(
@@ -498,7 +498,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
             }
         };
 
-        $app = $this->createAppWithoutFibersOrLogger(get_class($middleware));
+        $app = $this->createAppWithoutLogger(get_class($middleware));
 
         $app->get('/', function () {
             return new Response(
@@ -534,7 +534,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
             }
         };
 
-        $app = $this->createAppWithoutFibersOrLogger(get_class($middleware));
+        $app = $this->createAppWithoutLogger(get_class($middleware));
 
         $app->get('/', get_class($middleware), function (ServerRequestInterface $request) {
             return new Response(
@@ -562,7 +562,7 @@ public function __invoke(ServerRequestInterface $request, callable $next)
 
     public function testGlobalMiddlewareCallsNextWithModifiedRequestWillBeUsedForRouting()
     {
-        $app = $this->createAppWithoutFibersOrLogger(function (ServerRequestInterface $request, callable $next) {
+        $app = $this->createAppWithoutLogger(function (ServerRequestInterface $request, callable $next) {
             return $next($request->withUri($request->getUri()->withPath('/users')));
         });
 
@@ -592,7 +592,7 @@ public function testGlobalMiddlewareCallsNextWithModifiedRequestWillBeUsedForRou
 
     public function testGlobalMiddlewareCallsNextReturnsModifiedResponseWhenModifyingResponseFromRouter()
     {
-        $app = $this->createAppWithoutFibersOrLogger(function (ServerRequestInterface $request, callable $next) {
+        $app = $this->createAppWithoutLogger(function (ServerRequestInterface $request, callable $next) {
             $response = $next($request);
             assert($response instanceof ResponseInterface);
 
@@ -623,7 +623,7 @@ public function testGlobalMiddlewareCallsNextReturnsModifiedResponseWhenModifyin
 
     public function testGlobalMiddlewareReturnsResponseWithoutCallingNextReturnsResponseWithoutCallingRouter()
     {
-        $app = $this->createAppWithoutFibersOrLogger(function () {
+        $app = $this->createAppWithoutLogger(function () {
             return new Response(
                 200,
                 [
@@ -807,30 +807,4 @@ private function createAppWithoutLogger(...$middleware): App
 
         return $app;
     }
-
-    /** @param callable|class-string ...$middleware */
-    private function createAppWithoutFibersOrLogger(...$middleware): App
-    {
-        $app = new App(...$middleware);
-
-        $ref = new \ReflectionProperty($app, 'handler');
-        $ref->setAccessible(true);
-        $middleware = $ref->getValue($app);
-
-        $ref = new \ReflectionProperty($middleware, 'handlers');
-        $ref->setAccessible(true);
-        $handlers = $ref->getValue($middleware);
-
-        if (PHP_VERSION_ID >= 80100) {
-            $first = array_shift($handlers);
-            $this->assertInstanceOf(FiberHandler::class, $first);
-        }
-
-        $first = array_shift($handlers);
-        $this->assertInstanceOf(AccessLogHandler::class, $first);
-
-        $ref->setValue($middleware, $handlers);
-
-        return $app;
-    }
 }
diff --git a/tests/AppTest.php b/tests/AppTest.php
index 8261cdf..e527e02 100644
--- a/tests/AppTest.php
+++ b/tests/AppTest.php
@@ -27,6 +27,7 @@
 use React\EventLoop\Loop;
 use React\Http\Message\Response;
 use React\Http\Message\ServerRequest;
+use React\Promise\Deferred;
 use React\Promise\Promise;
 use React\Promise\PromiseInterface;
 use ReflectionMethod;
@@ -242,7 +243,7 @@ public function testRunAppWithBusyPortThrows()
 
     public function testRunOnceWillCreateRequestFromSapiThenRouteRequestAndThenSendResponseFromHandler()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $response = new Response();
         $app->get('/', function () use ($response) {
@@ -268,7 +269,7 @@ public function testRunOnceWillCreateRequestFromSapiThenRouteRequestAndThenSendR
 
     public function testRunOnceWillCreateRequestFromSapiThenRouteRequestAndThenSendResponseFromDeferredHandler()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $response = new Response();
         $app->get('/', function () use ($response) {
@@ -484,7 +485,7 @@ public function testRedirectMethodWithCustomRedirectCodeAddsAnyRouteOnRouterWhic
 
     public function testHandleRequestWithProxyRequestReturnsResponseWithMessageThatProxyRequestsAreNotAllowed()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $request = new ServerRequest('GET', 'http://google.com/');
         $request = $request->withRequestTarget('http://google.com/');
@@ -506,7 +507,7 @@ public function testHandleRequestWithProxyRequestReturnsResponseWithMessageThatP
 
     public function testHandleRequestWithUnknownRouteReturnsResponseWithFileNotFoundMessage()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $request = new ServerRequest('GET', 'http://localhost/invalid');
 
@@ -527,7 +528,7 @@ public function testHandleRequestWithUnknownRouteReturnsResponseWithFileNotFound
 
     public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithSingleMethodNotAllowedMessage()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users', function () { });
 
@@ -551,7 +552,7 @@ public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithSing
 
     public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithMultipleMethodNotAllowedMessage()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users', function () { });
         $app->head('/users', function () { });
@@ -577,7 +578,7 @@ public function testHandleRequestWithInvalidRequestMethodReturnsResponseWithMult
 
     public function testHandleRequestWithMatchingRouteReturnsResponseFromMatchingRouteHandler()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users', function () {
             return new Response(
@@ -605,7 +606,7 @@ public function testHandleRequestWithMatchingRouteReturnsResponseFromMatchingRou
 
     public function testHandleRequestWithOptionsAsteriskRequestReturnsResponseFromMatchingEmptyRouteHandler()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->options('', function () {
             return new Response(
@@ -698,7 +699,7 @@ public function testHandleRequestWithMatchingRouteReturnsPendingPromiseWhenHandl
 
     public function testHandleRequestWithMatchingRouteReturnsResponseWhenHandlerReturnsCoroutineWhichReturnsResponseWithoutYielding()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users', function () {
             if (false) {
@@ -837,46 +838,6 @@ public function testHandleRequestWithMatchingRouteReturnsPendingPromiseWhenHandl
         $this->assertFalse($resolved);
     }
 
-    public function testHandleRequestWithMatchingRouteReturnsPromiseResolvingWithResponseWhenHandlerReturnsResponse()
-    {
-        if (PHP_VERSION_ID < 80100) {
-            $this->markTestSkipped('Requires PHP 8.1+');
-        }
-
-        $app = $this->createAppWithoutLogger();
-
-        $app->get('/users', function () {
-            return new Response(
-                200,
-                [
-                    'Content-Type' => 'text/html'
-                ],
-                "OK\n"
-            );
-        });
-
-        $request = new ServerRequest('GET', 'http://localhost/users');
-
-        // $promise = $app->handleRequest($request);
-        $ref = new ReflectionMethod($app, 'handleRequest');
-        $ref->setAccessible(true);
-        $promise = $ref->invoke($app, $request);
-
-        /** @var PromiseInterface $promise */
-        $this->assertInstanceOf(PromiseInterface::class, $promise);
-
-        $response = null;
-        $promise->then(function ($value) use (&$response) {
-            $response = $value;
-        });
-
-        /** @var ResponseInterface $response */
-        $this->assertInstanceOf(ResponseInterface::class, $response);
-        $this->assertEquals(200, $response->getStatusCode());
-        $this->assertEquals('text/html', $response->getHeaderLine('Content-Type'));
-        $this->assertEquals("OK\n", (string) $response->getBody());
-    }
-
     public function testHandleRequestWithMatchingRouteReturnsPromiseResolvingWithResponseWhenHandlerReturnsResponseAfterAwaitingPromiseResolvingWithResponse()
     {
         if (PHP_VERSION_ID < 80100 || !function_exists('React\Async\async')) {
@@ -885,14 +846,10 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseResolvingWithRes
 
         $app = $this->createAppWithoutLogger();
 
-        $app->get('/users', function () {
-            return await(resolve(new Response(
-                200,
-                [
-                    'Content-Type' => 'text/html'
-                ],
-                "OK\n"
-            )));
+        $deferred = new Deferred();
+
+        $app->get('/users', function () use ($deferred) {
+            return await($deferred->promise());
         });
 
         $request = new ServerRequest('GET', 'http://localhost/users');
@@ -910,6 +867,21 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseResolvingWithRes
             $response = $value;
         });
 
+        $this->assertNull($response);
+
+        $deferred->resolve(new Response(
+            200,
+            [
+                'Content-Type' => 'text/html'
+            ],
+            "OK\n"
+        ));
+
+        // await next tick: https://github.com/reactphp/async/issues/27
+        await(new Promise(function ($resolve) {
+            Loop::futureTick($resolve);
+        }));
+
         /** @var ResponseInterface $response */
         $this->assertInstanceOf(ResponseInterface::class, $response);
         $this->assertEquals(200, $response->getStatusCode());
@@ -919,7 +891,7 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseResolvingWithRes
 
     public function testHandleRequestWithMatchingRouteAndRouteVariablesReturnsResponseFromHandlerWithRouteVariablesAssignedAsRequestAttributes()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users/{name}', function (ServerRequestInterface $request) {
             $name = $request->getAttribute('name');
@@ -949,7 +921,7 @@ public function testHandleRequestWithMatchingRouteAndRouteVariablesReturnsRespon
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerThrowsException()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $line = __LINE__ + 2;
         $app->get('/users', function () {
@@ -1080,7 +1052,7 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWit
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerReturnsCoroutineWhichThrowsExceptionWithoutYielding()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $line = __LINE__ + 5;
         $app->get('/users', function () {
@@ -1152,9 +1124,13 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWit
 
         $app = $this->createAppWithoutLogger();
 
-        $line = __LINE__ + 2;
-        $app->get('/users', function () {
-            return await(reject(new \RuntimeException('Foo')));
+        $deferred = new Deferred();
+
+        $line = __LINE__ + 1;
+        $exception = new \RuntimeException('Foo');
+
+        $app->get('/users', function () use ($deferred) {
+            return await($deferred->promise());
         });
 
         $request = new ServerRequest('GET', 'http://localhost/users');
@@ -1172,6 +1148,15 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWit
             $response = $value;
         });
 
+        $this->assertNull($response);
+
+        $deferred->reject($exception);
+
+        // await next tick: https://github.com/reactphp/async/issues/27
+        await(new Promise(function ($resolve) {
+            Loop::futureTick($resolve);
+        }));
+
         /** @var ResponseInterface $response */
         $this->assertInstanceOf(ResponseInterface::class, $response);
         $this->assertEquals(500, $response->getStatusCode());
@@ -1220,7 +1205,7 @@ public function testHandleRequestWithMatchingRouteReturnsPromiseWhichFulfillsWit
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerReturnsCoroutineWhichYieldsNullImmediately()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $line = __LINE__ + 3;
         $app->get('/users', function () {
@@ -1247,7 +1232,7 @@ public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResp
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerReturnsWrongValue()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users', function () {
             return null;
@@ -1273,7 +1258,7 @@ public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResp
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassDoesNotExist()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users', 'UnknownClass');
 
@@ -1364,7 +1349,7 @@ public function provideInvalidClasses()
      */
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassIsInvalid(string $class, string $error)
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $app->get('/users', $class);
 
@@ -1388,7 +1373,7 @@ public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResp
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassRequiresUnexpectedCallableParameter()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $line = __LINE__ + 2;
         $controller = new class {
@@ -1417,7 +1402,7 @@ public function __invoke(int $value) { }
 
     public function testHandleRequestWithMatchingRouteReturnsInternalServerErrorResponseWhenHandlerClassHasNoInvokeMethod()
     {
-        $app = $this->createAppWithoutFibersOrLogger();
+        $app = $this->createAppWithoutLogger();
 
         $controller = new class { };
 
@@ -1539,29 +1524,4 @@ private function createAppWithoutLogger(): App
 
         return $app;
     }
-
-    private function createAppWithoutFibersOrLogger(): App
-    {
-        $app = new App();
-
-        $ref = new \ReflectionProperty($app, 'handler');
-        $ref->setAccessible(true);
-        $middleware = $ref->getValue($app);
-
-        $ref = new \ReflectionProperty($middleware, 'handlers');
-        $ref->setAccessible(true);
-        $handlers = $ref->getValue($middleware);
-
-        if (PHP_VERSION_ID >= 80100) {
-            $first = array_shift($handlers);
-            $this->assertInstanceOf(FiberHandler::class, $first);
-        }
-
-        $first = array_shift($handlers);
-        $this->assertInstanceOf(AccessLogHandler::class, $first);
-
-        $ref->setValue($middleware, $handlers);
-
-        return $app;
-    }
 }
diff --git a/tests/FiberHandlerTest.php b/tests/FiberHandlerTest.php
index 8525c30..d388eec 100644
--- a/tests/FiberHandlerTest.php
+++ b/tests/FiberHandlerTest.php
@@ -23,22 +23,14 @@ public function setUp(): void
         }
     }
 
-    public function testInvokeWithHandlerReturningResponseReturnsPromiseResolvingWithSameResponse()
+    public function testInvokeWithHandlerReturningResponseReturnsSameResponse()
     {
         $handler = new FiberHandler();
 
         $request = new ServerRequest('GET', 'http://example.com/');
         $response = new Response();
 
-        $promise = $handler($request, function () use ($response) { return $response; });
-
-        /** @var PromiseInterface $promise */
-        $this->assertInstanceOf(PromiseInterface::class, $promise);
-
-        $ret = null;
-        $promise->then(function ($value) use (&$ret) {
-            $ret = $value;
-        });
+        $ret = $handler($request, function () use ($response) { return $response; });
 
         $this->assertSame($response, $ret);
     }
@@ -63,61 +55,54 @@ public function testInvokeWithHandlerReturningPromiseResolvingWithResponseReturn
         $this->assertSame($response, $ret);
     }
 
-    public function testInvokeWithHandlerReturningGeneratorReturningResponseReturnsPromiseResolvingWithSameResponse()
+    public function testInvokeWithHandlerReturningGeneratorReturningResponseReturnsGeneratorReturningSameResponse()
     {
         $handler = new FiberHandler();
 
         $request = new ServerRequest('GET', 'http://example.com/');
         $response = new Response();
 
-        $promise = $handler($request, function () use ($response) {
+        $generator = $handler($request, function () use ($response) {
             if (false) {
                 yield;
             }
             return $response;
         });
 
-        /** @var PromiseInterface $promise */
-        $this->assertInstanceOf(PromiseInterface::class, $promise);
-
-        $ret = null;
-        $promise->then(function ($value) use (&$ret) {
-            $ret = $value;
-        });
+        /** @var \Generator $generator */
+        $this->assertInstanceOf(\Generator::class, $generator);
+        $ret = $generator->getReturn();
 
         $this->assertSame($response, $ret);
     }
 
-    public function testInvokeWithHandlerReturningGeneratorReturningResponseAfterYieldingResolvedPromiseReturnsPromiseResolvingWithSameResponse()
+    public function testInvokeWithHandlerReturningGeneratorReturningResponseAfterYieldingResolvedPromiseReturnsGeneratorReturningSameResponse()
     {
         $handler = new FiberHandler();
 
         $request = new ServerRequest('GET', 'http://example.com/');
         $response = new Response();
 
-        $promise = $handler($request, function () use ($response) {
+        $generator = $handler($request, function () use ($response) {
             return yield resolve($response);
         });
 
-        /** @var PromiseInterface $promise */
-        $this->assertInstanceOf(PromiseInterface::class, $promise);
-
-        $ret = null;
-        $promise->then(function ($value) use (&$ret) {
-            $ret = $value;
-        });
+        /** @var \Generator $generator */
+        $this->assertInstanceOf(\Generator::class, $generator);
+        $generator->send($response);
+        $ret = $generator->getReturn();
 
         $this->assertSame($response, $ret);
     }
 
-    public function testInvokeWithHandlerReturningGeneratorReturningResponseAfterYieldingRejectedPromiseReturnsPromiseResolvingWithSameResponse()
+    public function testInvokeWithHandlerReturningGeneratorReturningResponseAfterYieldingRejectedPromiseReturnsGeneratorReturningSameResponse()
     {
         $handler = new FiberHandler();
 
         $request = new ServerRequest('GET', 'http://example.com/');
         $response = new Response();
 
-        $promise = $handler($request, function () use ($response) {
+        $generator = $handler($request, function () use ($response) {
             try {
                 yield reject(new \RuntimeException('Foo'));
             } catch (\RuntimeException $e) {
@@ -125,36 +110,25 @@ public function testInvokeWithHandlerReturningGeneratorReturningResponseAfterYie
             }
         });
 
-        /** @var PromiseInterface $promise */
-        $this->assertInstanceOf(PromiseInterface::class, $promise);
-
-        $ret = null;
-        $promise->then(function ($value) use (&$ret) {
-            $ret = $value;
-        });
+        /** @var \Generator $generator */
+        $this->assertInstanceOf(\Generator::class, $generator);
+        $generator->throw(new \RuntimeException('Foo'));
+        $ret = $generator->getReturn();
 
         $this->assertSame($response, $ret);
     }
 
-    public function testInvokeWithHandlerReturningResponseAfterAwaitingResolvedPromiseReturnsPromiseResolvingWithSameResponse()
+    public function testInvokeWithHandlerReturningResponseAfterAwaitingResolvedPromiseReturnsSameResponse()
     {
         $handler = new FiberHandler();
 
         $request = new ServerRequest('GET', 'http://example.com/');
         $response = new Response();
 
-        $promise = $handler($request, function () use ($response) {
+        $ret = $handler($request, function () use ($response) {
             return await(resolve($response));
         });
 
-        /** @var PromiseInterface $promise */
-        $this->assertInstanceOf(PromiseInterface::class, $promise);
-
-        $ret = null;
-        $promise->then(function ($value) use (&$ret) {
-            $ret = $value;
-        });
-
         $this->assertSame($response, $ret);
     }