diff --git a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
index 6972de48cc..5eb9179d7f 100644
--- a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
+++ b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php
@@ -319,7 +319,7 @@ class DeprecationErrorHandler
     private static function getPhpUnitErrorHandler()
     {
         if (!isset(self::$isAtLeastPhpUnit83)) {
-            self::$isAtLeastPhpUnit83 = class_exists(ErrorHandler::class) && method_exists(ErrorHandler::class, '__invoke');
+            self::$isAtLeastPhpUnit83 = class_exists('PHPUnit\Util\ErrorHandler') && method_exists('PHPUnit\Util\ErrorHandler', '__invoke');
         }
         if (!self::$isAtLeastPhpUnit83) {
             return 'PHPUnit\Util\ErrorHandler::handleError';
diff --git a/src/Symfony/Bundle/FrameworkBundle/Command/AboutCommand.php b/src/Symfony/Bundle/FrameworkBundle/Command/AboutCommand.php
index 7753f1b25f..cf3e946f6a 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Command/AboutCommand.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Command/AboutCommand.php
@@ -131,9 +131,9 @@ EOT
     private static function getDotenvVars(): array
     {
         $vars = [];
-        foreach (explode(',', getenv('SYMFONY_DOTENV_VARS')) as $name) {
-            if ('' !== $name && false !== $value = getenv($name)) {
-                $vars[$name] = $value;
+        foreach (explode(',', $_SERVER['SYMFONY_DOTENV_VARS'] ?? $_ENV['SYMFONY_DOTENV_VARS'] ?? '') as $name) {
+            if ('' !== $name && isset($_ENV[$name])) {
+                $vars[$name] = $_ENV[$name];
             }
         }
 
diff --git a/src/Symfony/Component/BrowserKit/HttpBrowser.php b/src/Symfony/Component/BrowserKit/HttpBrowser.php
index d36cf23712..b2331ea492 100644
--- a/src/Symfony/Component/BrowserKit/HttpBrowser.php
+++ b/src/Symfony/Component/BrowserKit/HttpBrowser.php
@@ -23,8 +23,6 @@ use Symfony\Contracts\HttpClient\HttpClientInterface;
  * to make real HTTP requests.
  *
  * @author Fabien Potencier <fabien@symfony.com>
- *
- * @final
  */
 class HttpBrowser extends AbstractBrowser
 {
@@ -32,7 +30,7 @@ class HttpBrowser extends AbstractBrowser
 
     public function __construct(HttpClientInterface $client = null, History $history = null, CookieJar $cookieJar = null)
     {
-        if (!class_exists(HttpClient::class)) {
+        if (!$client && !class_exists(HttpClient::class)) {
             throw new \LogicException(sprintf('You cannot use "%s" as the HttpClient component is not installed. Try running "composer require symfony/http-client".', __CLASS__));
         }
 
diff --git a/src/Symfony/Component/DomCrawler/Field/ChoiceFormField.php b/src/Symfony/Component/DomCrawler/Field/ChoiceFormField.php
index 6539bfff66..8b437630d0 100644
--- a/src/Symfony/Component/DomCrawler/Field/ChoiceFormField.php
+++ b/src/Symfony/Component/DomCrawler/Field/ChoiceFormField.php
@@ -113,7 +113,7 @@ class ChoiceFormField extends FormField
     /**
      * Sets the value of the field.
      *
-     * @param string|array $value The value of the field
+     * @param string|array|bool $value The value of the field
      *
      * @throws \InvalidArgumentException When value type provided is not correct
      */
diff --git a/src/Symfony/Component/DomCrawler/Field/FileFormField.php b/src/Symfony/Component/DomCrawler/Field/FileFormField.php
index 9e21c9c4b9..9abdca8827 100644
--- a/src/Symfony/Component/DomCrawler/Field/FileFormField.php
+++ b/src/Symfony/Component/DomCrawler/Field/FileFormField.php
@@ -48,7 +48,7 @@ class FileFormField extends FormField
     /**
      * Sets the value of the field.
      *
-     * @param string $value The value of the field
+     * @param string|null $value The value of the field
      */
     public function setValue($value)
     {
diff --git a/src/Symfony/Component/DomCrawler/Field/FormField.php b/src/Symfony/Component/DomCrawler/Field/FormField.php
index 51d875514c..0bc4f54479 100644
--- a/src/Symfony/Component/DomCrawler/Field/FormField.php
+++ b/src/Symfony/Component/DomCrawler/Field/FormField.php
@@ -99,7 +99,7 @@ abstract class FormField
     /**
      * Sets the value of the field.
      *
-     * @param string $value The value of the field
+     * @param string|array|bool|null $value The value of the field
      */
     public function setValue($value)
     {
diff --git a/src/Symfony/Component/Finder/Iterator/SortableIterator.php b/src/Symfony/Component/Finder/Iterator/SortableIterator.php
index cc955a7108..479489367a 100644
--- a/src/Symfony/Component/Finder/Iterator/SortableIterator.php
+++ b/src/Symfony/Component/Finder/Iterator/SortableIterator.php
@@ -41,15 +41,15 @@ class SortableIterator implements \IteratorAggregate
         $order = $reverseOrder ? -1 : 1;
 
         if (self::SORT_BY_NAME === $sort) {
-            $this->sort = function ($a, $b) use ($order) {
+            $this->sort = static function ($a, $b) use ($order) {
                 return $order * strcmp($a->getRealPath() ?: $a->getPathname(), $b->getRealPath() ?: $b->getPathname());
             };
         } elseif (self::SORT_BY_NAME_NATURAL === $sort) {
-            $this->sort = function ($a, $b) use ($order) {
+            $this->sort = static function ($a, $b) use ($order) {
                 return $order * strnatcmp($a->getRealPath() ?: $a->getPathname(), $b->getRealPath() ?: $b->getPathname());
             };
         } elseif (self::SORT_BY_TYPE === $sort) {
-            $this->sort = function ($a, $b) use ($order) {
+            $this->sort = static function ($a, $b) use ($order) {
                 if ($a->isDir() && $b->isFile()) {
                     return -$order;
                 } elseif ($a->isFile() && $b->isDir()) {
@@ -59,15 +59,15 @@ class SortableIterator implements \IteratorAggregate
                 return $order * strcmp($a->getRealPath() ?: $a->getPathname(), $b->getRealPath() ?: $b->getPathname());
             };
         } elseif (self::SORT_BY_ACCESSED_TIME === $sort) {
-            $this->sort = function ($a, $b) use ($order) {
+            $this->sort = static function ($a, $b) use ($order) {
                 return $order * ($a->getATime() - $b->getATime());
             };
         } elseif (self::SORT_BY_CHANGED_TIME === $sort) {
-            $this->sort = function ($a, $b) use ($order) {
+            $this->sort = static function ($a, $b) use ($order) {
                 return $order * ($a->getCTime() - $b->getCTime());
             };
         } elseif (self::SORT_BY_MODIFIED_TIME === $sort) {
-            $this->sort = function ($a, $b) use ($order) {
+            $this->sort = static function ($a, $b) use ($order) {
                 return $order * ($a->getMTime() - $b->getMTime());
             };
         } elseif (self::SORT_BY_NONE === $sort) {
diff --git a/src/Symfony/Component/HttpKernel/Kernel.php b/src/Symfony/Component/HttpKernel/Kernel.php
index d2ef8515b4..c4096308ca 100644
--- a/src/Symfony/Component/HttpKernel/Kernel.php
+++ b/src/Symfony/Component/HttpKernel/Kernel.php
@@ -356,7 +356,12 @@ abstract class Kernel implements KernelInterface, RebootableInterface, Terminabl
     {
         if (null === $this->projectDir) {
             $r = new \ReflectionObject($this);
-            $dir = $rootDir = \dirname($r->getFileName());
+
+            if (!file_exists($dir = $r->getFileName())) {
+                throw new \LogicException(sprintf('Cannot auto-detect project dir for kernel of class "%s".', $r->name));
+            }
+
+            $dir = $rootDir = \dirname($dir);
             while (!file_exists($dir.'/composer.json')) {
                 if ($dir === \dirname($dir)) {
                     return $this->projectDir = $rootDir;
diff --git a/src/Symfony/Component/HttpKernel/Tests/Fixtures/KernelForTest.php b/src/Symfony/Component/HttpKernel/Tests/Fixtures/KernelForTest.php
index 5ba41ce038..f3b1951b83 100644
--- a/src/Symfony/Component/HttpKernel/Tests/Fixtures/KernelForTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/Fixtures/KernelForTest.php
@@ -36,13 +36,8 @@ class KernelForTest extends Kernel
         return $this->booted;
     }
 
-    public function getCacheDir(): string
+    public function getProjectDir(): string
     {
-        return $this->getProjectDir().'/Tests/Fixtures/cache.'.$this->environment;
-    }
-
-    public function getLogDir(): string
-    {
-        return $this->getProjectDir().'/Tests/Fixtures/logs';
+        return __DIR__;
     }
 }
diff --git a/src/Symfony/Component/HttpKernel/Tests/KernelTest.php b/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
index 238b46a8dc..065a3ea148 100644
--- a/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
@@ -129,7 +129,7 @@ class KernelTest extends TestCase
     public function testBootSetsTheBootedFlagToTrue()
     {
         // use test kernel to access isBooted()
-        $kernel = $this->getKernelForTest(['initializeBundles', 'initializeContainer']);
+        $kernel = $this->getKernel(['initializeBundles', 'initializeContainer']);
         $kernel->boot();
 
         $this->assertTrue($kernel->isBooted());
@@ -608,7 +608,7 @@ EOF;
      */
     public function testKernelStartTimeIsResetWhileBootingAlreadyBootedKernel()
     {
-        $kernel = $this->getKernelForTest(['initializeBundles'], true);
+        $kernel = $this->getKernel(['initializeBundles'], [], true);
         $kernel->boot();
         $preReBoot = $kernel->getStartTime();
 
@@ -656,36 +656,20 @@ EOF;
      * @param array $methods Additional methods to mock (besides the abstract ones)
      * @param array $bundles Bundles to register
      */
-    protected function getKernel(array $methods = [], array $bundles = []): Kernel
+    protected function getKernel(array $methods = [], array $bundles = [], bool $debug = false): Kernel
     {
         $methods[] = 'registerBundles';
 
         $kernel = $this
-            ->getMockBuilder('Symfony\Component\HttpKernel\Kernel')
+            ->getMockBuilder(KernelForTest::class)
             ->setMethods($methods)
-            ->setConstructorArgs(['test', false])
-            ->getMockForAbstractClass()
+            ->setConstructorArgs(['test', $debug])
+            ->getMock()
         ;
         $kernel->expects($this->any())
             ->method('registerBundles')
             ->willReturn($bundles)
         ;
-        $p = new \ReflectionProperty($kernel, 'rootDir');
-        $p->setAccessible(true);
-        $p->setValue($kernel, __DIR__.'/Fixtures');
-
-        return $kernel;
-    }
-
-    protected function getKernelForTest(array $methods = [], $debug = false)
-    {
-        $kernel = $this->getMockBuilder('Symfony\Component\HttpKernel\Tests\Fixtures\KernelForTest')
-            ->setConstructorArgs(['test', $debug])
-            ->setMethods($methods)
-            ->getMock();
-        $p = new \ReflectionProperty($kernel, 'rootDir');
-        $p->setAccessible(true);
-        $p->setValue($kernel, __DIR__.'/Fixtures');
 
         return $kernel;
     }
@@ -703,6 +687,11 @@ class TestKernel implements HttpKernelInterface
     public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = true): Response
     {
     }
+
+    public function getProjectDir(): string
+    {
+        return __DIR__.'/Fixtures';
+    }
 }
 
 class CustomProjectDirKernel extends Kernel
diff --git a/src/Symfony/Component/Lock/Tests/Store/BlockingStoreTestTrait.php b/src/Symfony/Component/Lock/Tests/Store/BlockingStoreTestTrait.php
index 9c9ecdcd2f..55d8d34c86 100644
--- a/src/Symfony/Component/Lock/Tests/Store/BlockingStoreTestTrait.php
+++ b/src/Symfony/Component/Lock/Tests/Store/BlockingStoreTestTrait.php
@@ -33,6 +33,10 @@ trait BlockingStoreTestTrait
      *
      * This test is time sensible: the $clockDelay could be adjust.
      *
+     * It also fails when run with the global ./phpunit test suite.
+     *
+     * @group transient
+     *
      * @requires extension pcntl
      * @requires extension posix
      * @requires function pcntl_sigwaitinfo
diff --git a/src/Symfony/Component/Mailer/Transport/AbstractTransport.php b/src/Symfony/Component/Mailer/Transport/AbstractTransport.php
index 71d7636d06..fb817f75b5 100644
--- a/src/Symfony/Component/Mailer/Transport/AbstractTransport.php
+++ b/src/Symfony/Component/Mailer/Transport/AbstractTransport.php
@@ -13,7 +13,6 @@ namespace Symfony\Component\Mailer\Transport;
 
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
-use Symfony\Component\EventDispatcher\EventDispatcher;
 use Symfony\Component\Mailer\DelayedSmtpEnvelope;
 use Symfony\Component\Mailer\Event\MessageEvent;
 use Symfony\Component\Mailer\Exception\TransportException;
@@ -35,7 +34,7 @@ abstract class AbstractTransport implements TransportInterface
 
     public function __construct(EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
-        $this->dispatcher = $dispatcher ?: new EventDispatcher();
+        $this->dispatcher = $dispatcher;
         $this->logger = $logger ?: new NullLogger();
     }
 
@@ -67,14 +66,17 @@ abstract class AbstractTransport implements TransportInterface
             }
         }
 
-        $event = new MessageEvent($message, $envelope, (string) $this);
-        $this->dispatcher->dispatch($event);
-        $envelope = $event->getEnvelope();
+        if (null !== $this->dispatcher) {
+            $event = new MessageEvent($message, $envelope, (string) $this);
+            $this->dispatcher->dispatch($event);
+            $envelope = $event->getEnvelope();
+        }
+
         if (!$envelope->getRecipients()) {
             return null;
         }
 
-        $message = new SentMessage($event->getMessage(), $envelope);
+        $message = new SentMessage($message, $envelope);
         $this->doSend($message);
 
         $this->checkThrottling();
diff --git a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/ConnectionTest.php b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/ConnectionTest.php
index 2869ccbe8b..08f93b0393 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/ConnectionTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/RedisExt/ConnectionTest.php
@@ -20,6 +20,21 @@ use Symfony\Component\Messenger\Transport\RedisExt\Connection;
  */
 class ConnectionTest extends TestCase
 {
+    public static function setUpBeforeClass()
+    {
+        $redis = Connection::fromDsn('redis://localhost/queue');
+
+        try {
+            $redis->get();
+        } catch (TransportException $e) {
+            if (0 === strpos($e->getMessage(), 'ERR unknown command \'X')) {
+                self::markTestSkipped('Redis server >= 5 is required');
+            }
+
+            throw $e;
+        }
+    }
+
     public function testFromInvalidDsn()
     {
         $this->expectException(\InvalidArgumentException::class);
diff --git a/src/Symfony/Component/Serializer/Tests/Encoder/ChainEncoderTest.php b/src/Symfony/Component/Serializer/Tests/Encoder/ChainEncoderTest.php
index 4b97fdf534..82aa2934d9 100644
--- a/src/Symfony/Component/Serializer/Tests/Encoder/ChainEncoderTest.php
+++ b/src/Symfony/Component/Serializer/Tests/Encoder/ChainEncoderTest.php
@@ -84,23 +84,6 @@ class ChainEncoderTest extends TestCase
         $this->assertTrue($this->chainEncoder->needsNormalization(self::FORMAT_2));
     }
 
-    /**
-     * @dataProvider booleanProvider
-     */
-    public function testNeedsNormalizationChainNormalizationAware($bool)
-    {
-        $chainEncoder = $this
-            ->getMockBuilder('Symfony\Component\Serializer\Tests\Encoder\ChainNormalizationAwareEncoder')
-            ->getMock();
-
-        $chainEncoder->method('supportsEncoding')->willReturn(true);
-        $chainEncoder->method('needsNormalization')->willReturn($bool);
-
-        $sut = new ChainEncoder([$chainEncoder]);
-
-        $this->assertEquals($bool, $sut->needsNormalization(self::FORMAT_1));
-    }
-
     public function testNeedsNormalizationNormalizationAware()
     {
         $encoder = new NormalizationAwareEncoder();
@@ -108,18 +91,6 @@ class ChainEncoderTest extends TestCase
 
         $this->assertFalse($sut->needsNormalization(self::FORMAT_1));
     }
-
-    public function booleanProvider()
-    {
-        return [
-            [true],
-            [false],
-        ];
-    }
-}
-
-class ChainNormalizationAwareEncoder extends ChainEncoder implements NormalizationAwareInterface
-{
 }
 
 class NormalizationAwareEncoder implements EncoderInterface, NormalizationAwareInterface