diff --git a/composer.lock b/composer.lock
index 26bc91aaa4..c43e82677e 100644
--- a/composer.lock
+++ b/composer.lock
@@ -2060,7 +2060,7 @@
                 },
                 {
                     "name": "Gert de Pagter",
-                    "email": "backendtea@gmail.com"
+                    "email": "BackEndTea@gmail.com"
                 }
             ],
             "description": "Symfony polyfill for ctype functions",
@@ -3326,6 +3326,246 @@
             ],
             "time": "2018-01-07T19:17:08+00:00"
         },
+        {
+            "name": "composer/ca-bundle",
+            "version": "1.1.4",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/composer/ca-bundle.git",
+                "reference": "558f321c52faeb4828c03e7dc0cfe39a09e09a2d"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/composer/ca-bundle/zipball/558f321c52faeb4828c03e7dc0cfe39a09e09a2d",
+                "reference": "558f321c52faeb4828c03e7dc0cfe39a09e09a2d",
+                "shasum": ""
+            },
+            "require": {
+                "ext-openssl": "*",
+                "ext-pcre": "*",
+                "php": "^5.3.2 || ^7.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.8.35 || ^5.7 || ^6.5",
+                "psr/log": "^1.0",
+                "symfony/process": "^2.5 || ^3.0 || ^4.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Composer\\CaBundle\\": "src"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Jordi Boggiano",
+                    "email": "j.boggiano@seld.be",
+                    "homepage": "http://seld.be"
+                }
+            ],
+            "description": "Lets you find a path to the system CA bundle, and includes a fallback to the Mozilla CA bundle.",
+            "keywords": [
+                "cabundle",
+                "cacert",
+                "certificate",
+                "ssl",
+                "tls"
+            ],
+            "time": "2019-01-28T09:30:10+00:00"
+        },
+        {
+            "name": "composer/composer",
+            "version": "1.8.5",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/composer/composer.git",
+                "reference": "949b116f9e7d98d8d276594fed74b580d125c0e6"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/composer/composer/zipball/949b116f9e7d98d8d276594fed74b580d125c0e6",
+                "reference": "949b116f9e7d98d8d276594fed74b580d125c0e6",
+                "shasum": ""
+            },
+            "require": {
+                "composer/ca-bundle": "^1.0",
+                "composer/semver": "^1.0",
+                "composer/spdx-licenses": "^1.2",
+                "composer/xdebug-handler": "^1.1",
+                "justinrainbow/json-schema": "^3.0 || ^4.0 || ^5.0",
+                "php": "^5.3.2 || ^7.0",
+                "psr/log": "^1.0",
+                "seld/jsonlint": "^1.4",
+                "seld/phar-utils": "^1.0",
+                "symfony/console": "^2.7 || ^3.0 || ^4.0",
+                "symfony/filesystem": "^2.7 || ^3.0 || ^4.0",
+                "symfony/finder": "^2.7 || ^3.0 || ^4.0",
+                "symfony/process": "^2.7 || ^3.0 || ^4.0"
+            },
+            "conflict": {
+                "symfony/console": "2.8.38"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.8.35 || ^5.7",
+                "phpunit/phpunit-mock-objects": "^2.3 || ^3.0"
+            },
+            "suggest": {
+                "ext-openssl": "Enabling the openssl extension allows you to access https URLs for repositories and packages",
+                "ext-zip": "Enabling the zip extension allows you to unzip archives",
+                "ext-zlib": "Allow gzip compression of HTTP requests"
+            },
+            "bin": [
+                "bin/composer"
+            ],
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.8-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Composer\\": "src/Composer"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nils Adermann",
+                    "email": "naderman@naderman.de",
+                    "homepage": "http://www.naderman.de"
+                },
+                {
+                    "name": "Jordi Boggiano",
+                    "email": "j.boggiano@seld.be",
+                    "homepage": "http://seld.be"
+                }
+            ],
+            "description": "Composer helps you declare, manage and install dependencies of PHP projects, ensuring you have the right stack everywhere.",
+            "homepage": "https://getcomposer.org/",
+            "keywords": [
+                "autoload",
+                "dependency",
+                "package"
+            ],
+            "time": "2019-04-09T15:46:48+00:00"
+        },
+        {
+            "name": "composer/spdx-licenses",
+            "version": "1.5.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/composer/spdx-licenses.git",
+                "reference": "a1aa51cf3ab838b83b0867b14e56fc20fbd55b3d"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/composer/spdx-licenses/zipball/a1aa51cf3ab838b83b0867b14e56fc20fbd55b3d",
+                "reference": "a1aa51cf3ab838b83b0867b14e56fc20fbd55b3d",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.3.2 || ^7.0 || ^8.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.8.35 || ^5.7 || 6.5 - 7"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Composer\\Spdx\\": "src"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nils Adermann",
+                    "email": "naderman@naderman.de",
+                    "homepage": "http://www.naderman.de"
+                },
+                {
+                    "name": "Jordi Boggiano",
+                    "email": "j.boggiano@seld.be",
+                    "homepage": "http://seld.be"
+                },
+                {
+                    "name": "Rob Bast",
+                    "email": "rob.bast@gmail.com",
+                    "homepage": "http://robbast.nl"
+                }
+            ],
+            "description": "SPDX licenses list and validation library.",
+            "keywords": [
+                "license",
+                "spdx",
+                "validator"
+            ],
+            "time": "2019-03-26T10:23:26+00:00"
+        },
+        {
+            "name": "composer/xdebug-handler",
+            "version": "1.3.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/composer/xdebug-handler.git",
+                "reference": "46867cbf8ca9fb8d60c506895449eb799db1184f"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/composer/xdebug-handler/zipball/46867cbf8ca9fb8d60c506895449eb799db1184f",
+                "reference": "46867cbf8ca9fb8d60c506895449eb799db1184f",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.3.2 || ^7.0",
+                "psr/log": "^1.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.8.35 || ^5.7 || ^6.5"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Composer\\XdebugHandler\\": "src"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "John Stevenson",
+                    "email": "john-stevenson@blueyonder.co.uk"
+                }
+            ],
+            "description": "Restarts a process without xdebug.",
+            "keywords": [
+                "Xdebug",
+                "performance"
+            ],
+            "time": "2019-05-27T17:52:04+00:00"
+        },
         {
             "name": "doctrine/instantiator",
             "version": "1.0.5",
@@ -5011,6 +5251,99 @@
             "homepage": "https://github.com/sebastianbergmann/version",
             "time": "2016-10-03T07:35:21+00:00"
         },
+        {
+            "name": "seld/jsonlint",
+            "version": "1.7.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/Seldaek/jsonlint.git",
+                "reference": "d15f59a67ff805a44c50ea0516d2341740f81a38"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/Seldaek/jsonlint/zipball/d15f59a67ff805a44c50ea0516d2341740f81a38",
+                "reference": "d15f59a67ff805a44c50ea0516d2341740f81a38",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.3 || ^7.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.8.35 || ^5.7 || ^6.0"
+            },
+            "bin": [
+                "bin/jsonlint"
+            ],
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Seld\\JsonLint\\": "src/Seld/JsonLint/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Jordi Boggiano",
+                    "email": "j.boggiano@seld.be",
+                    "homepage": "http://seld.be"
+                }
+            ],
+            "description": "JSON Linter",
+            "keywords": [
+                "json",
+                "linter",
+                "parser",
+                "validator"
+            ],
+            "time": "2018-01-24T12:46:19+00:00"
+        },
+        {
+            "name": "seld/phar-utils",
+            "version": "1.0.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/Seldaek/phar-utils.git",
+                "reference": "7009b5139491975ef6486545a39f3e6dad5ac30a"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/Seldaek/phar-utils/zipball/7009b5139491975ef6486545a39f3e6dad5ac30a",
+                "reference": "7009b5139491975ef6486545a39f3e6dad5ac30a",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Seld\\PharUtils\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Jordi Boggiano",
+                    "email": "j.boggiano@seld.be"
+                }
+            ],
+            "description": "PHAR file format utilities, for when PHP phars you up",
+            "keywords": [
+                "phra"
+            ],
+            "time": "2015-10-13T18:44:15+00:00"
+        },
         {
             "name": "squizlabs/php_codesniffer",
             "version": "3.4.2",
@@ -5229,6 +5562,105 @@
             "homepage": "https://symfony.com",
             "time": "2019-02-23T15:06:07+00:00"
         },
+        {
+            "name": "symfony/filesystem",
+            "version": "v3.4.28",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/filesystem.git",
+                "reference": "acf99758b1df8e9295e6b85aa69f294565c9fedb"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/filesystem/zipball/acf99758b1df8e9295e6b85aa69f294565c9fedb",
+                "reference": "acf99758b1df8e9295e6b85aa69f294565c9fedb",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.5.9|>=7.0.8",
+                "symfony/polyfill-ctype": "~1.8"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "3.4-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Filesystem\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony Filesystem Component",
+            "homepage": "https://symfony.com",
+            "time": "2019-02-04T21:34:32+00:00"
+        },
+        {
+            "name": "symfony/finder",
+            "version": "v3.4.28",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/finder.git",
+                "reference": "fa5d962a71f2169dfe1cbae217fa5a2799859f6c"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/finder/zipball/fa5d962a71f2169dfe1cbae217fa5a2799859f6c",
+                "reference": "fa5d962a71f2169dfe1cbae217fa5a2799859f6c",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.5.9|>=7.0.8"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "3.4-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Finder\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony Finder Component",
+            "homepage": "https://symfony.com",
+            "time": "2019-05-24T12:25:55+00:00"
+        },
         {
             "name": "symfony/phpunit-bridge",
             "version": "v3.4.26",
diff --git a/core/composer.json b/core/composer.json
index e5de4f6b2c..b843f2869c 100644
--- a/core/composer.json
+++ b/core/composer.json
@@ -56,6 +56,7 @@
         "behat/mink": "1.7.x-dev",
         "behat/mink-goutte-driver": "^1.2",
         "behat/mink-selenium2-driver": "1.3.x-dev",
+        "composer/composer": "^1.8",
         "drupal/coder": "^8.3.2",
         "jcalderonzumba/gastonjs": "^1.0.2",
         "jcalderonzumba/mink-phantomjs-driver": "^0.3.1",
diff --git a/core/lib/Drupal/Component/VendorCleanup/Config.php b/core/lib/Drupal/Component/VendorCleanup/Config.php
new file mode 100644
index 0000000000..ba62a9aeec
--- /dev/null
+++ b/core/lib/Drupal/Component/VendorCleanup/Config.php
@@ -0,0 +1,172 @@
+<?php
+
+namespace Drupal\Component\VendorCleanup;
+
+use Composer\Package\RootPackageInterface;
+
+/**
+ * Determine configuration.
+ *
+ * Default configuration is merged with the root package's
+ * extra:drupal-core-vendor-cleanup configuration.
+ */
+class Config {
+
+  /**
+   * The default configuration which will always be merged with user config.
+   *
+   * @var array
+   */
+  protected static $defaultConfig = [
+    'behat/mink' => ['tests', 'driver-testsuite'],
+    'behat/mink-browserkit-driver' => ['tests'],
+    'behat/mink-goutte-driver' => ['tests'],
+    'brumann/polyfill-unserialize' => ['tests'],
+    'drupal/coder' => [
+      'coder_sniffer/Drupal/Test',
+      'coder_sniffer/DrupalPractice/Test',
+    ],
+    'doctrine/cache' => ['tests'],
+    'doctrine/collections' => ['tests'],
+    'doctrine/common' => ['tests'],
+    'doctrine/inflector' => ['tests'],
+    'doctrine/instantiator' => ['tests'],
+    'egulias/email-validator' => ['documentation', 'tests'],
+    'fabpot/goutte' => ['Goutte/Tests'],
+    'guzzlehttp/promises' => ['tests'],
+    'guzzlehttp/psr7' => ['tests'],
+    'jcalderonzumba/gastonjs' => ['docs', 'examples', 'tests'],
+    'jcalderonzumba/mink-phantomjs-driver' => ['tests'],
+    'masterminds/html5' => ['test'],
+    'mikey179/vfsStream' => ['src/test'],
+    'paragonie/random_compat' => ['tests'],
+    'pear/archive_tar' => ['tests'],
+    'pear/console_getopt' => ['tests'],
+    'pear/pear-core-minimal' => ['tests'],
+    'pear/pear_exception' => ['tests'],
+    'phpdocumentor/reflection-docblock' => ['tests'],
+    'phpunit/php-code-coverage' => ['tests'],
+    'phpunit/php-timer' => ['tests'],
+    'phpunit/php-token-stream' => ['tests'],
+    'phpunit/phpunit' => ['tests'],
+    'phpunit/php-mock-objects' => ['tests'],
+    'sebastian/comparator' => ['tests'],
+    'sebastian/diff' => ['tests'],
+    'sebastian/environment' => ['tests'],
+    'sebastian/exporter' => ['tests'],
+    'sebastian/global-state' => ['tests'],
+    'sebastian/recursion-context' => ['tests'],
+    'stack/builder' => ['tests'],
+    'symfony/browser-kit' => ['Tests'],
+    'symfony/class-loader' => ['Tests'],
+    'symfony/console' => ['Tests'],
+    'symfony/css-selector' => ['Tests'],
+    'symfony/debug' => ['Tests'],
+    'symfony/dependency-injection' => ['Tests'],
+    'symfony/dom-crawler' => ['Tests'],
+    // @todo Add symfony/event-dispatcher during
+    //   https://www.drupal.org/project/drupal/issues/3055040
+    'symfony/http-foundation' => ['Tests'],
+    'symfony/http-kernel' => ['Tests'],
+    'symfony/process' => ['Tests'],
+    'symfony/psr-http-message-bridge' => ['Tests'],
+    'symfony/routing' => ['Tests'],
+    'symfony/serializer' => ['Tests'],
+    'symfony/translation' => ['Tests'],
+    'symfony/validator' => ['Tests', 'Resources'],
+    'symfony/yaml' => ['Tests'],
+    'symfony-cmf/routing' => ['Test', 'Tests'],
+    'twig/twig' => ['doc', 'ext', 'test'],
+  ];
+
+  /**
+   * The root package.
+   *
+   * @var Composer\Package\RootPackageInterface
+   */
+  protected $rootPackage;
+
+  /**
+   * Configuration gleaned from the root package.
+   *
+   * @var array
+   */
+  protected $configData = [];
+
+  public function __construct(RootPackageInterface $root_package) {
+    $this->rootPackage = $root_package;
+  }
+
+  /**
+   * Get the configuration from the root package.
+   *
+   * This is stored in composer.json extra:drupal-core-vendor-cleanup.
+   *
+   * @return []
+   *   An array keyed by package name. Each array value is an array of paths,
+   *   relative to the package.
+   */
+  protected function getPluginConfig() {
+    if ($this->configData) {
+      return $this->configData;
+    }
+    // Get the root package config.
+    $package_config = $this->rootPackage->getExtra();
+    if (isset($package_config['drupal-core-vendor-cleanup'])) {
+      $this->configData = $package_config['drupal-core-vendor-cleanup'];
+    }
+    // Ensure the values are arrays.
+    foreach ($this->configData as $package => $paths) {
+      if (!is_array($paths)) {
+        $this->configData[$package] = [$paths];
+      }
+    }
+    // Merge root config with defaults.
+    foreach (static::$defaultConfig as $package => $paths) {
+      if (isset($this->configData[$package])) {
+        $this->configData[$package] = array_merge($this->configData[$package], $paths);
+      }
+      else {
+        $this->configData[$package] = $paths;
+      }
+    }
+    return $this->configData;
+  }
+
+  /**
+   * Get a list of paths to remove for the given package.
+   *
+   * @param string $package
+   *   The package name.
+   *
+   * @return string[]
+   *   Array of paths to remove, relative to the package.
+   */
+  public function getPathsForPackage($package) {
+    $paths = [];
+    $config = $this->getPluginConfig();
+    if (isset($config[$package])) {
+      $paths = $config[$package];
+    }
+    else {
+      // Handle any mismatch in case between the package name and array key. For
+      // example, the array key 'mikey179/vfsStream' needs to be found when
+      // composer returns a package name of 'mikey179/vfsstream'.
+      foreach (array_keys($config) as $key) {
+        if (strtolower($key) == strtolower($package)) {
+          $paths = $config[$key];
+          break;
+        }
+      }
+    }
+    return $paths;
+  }
+
+  /**
+   * If there is no configuration in the root package, it is unconfigured.
+   */
+  public function isUnconfigured() {
+    return empty($this->getPluginConfig());
+  }
+
+}
diff --git a/core/lib/Drupal/Component/VendorCleanup/LICENSE.txt b/core/lib/Drupal/Component/VendorCleanup/LICENSE.txt
new file mode 100644
index 0000000000..94fb84639c
--- /dev/null
+++ b/core/lib/Drupal/Component/VendorCleanup/LICENSE.txt
@@ -0,0 +1,339 @@
+        GNU GENERAL PUBLIC LICENSE
+           Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+          Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+        GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+    a) Accompany it with the complete corresponding machine-readable
+    source code, which must be distributed under the terms of Sections
+    1 and 2 above on a medium customarily used for software interchange; or,
+
+    b) Accompany it with a written offer, valid for at least three
+    years, to give any third party, for a charge no more than your
+    cost of physically performing source distribution, a complete
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+    customarily used for software interchange; or,
+
+    c) Accompany it with the information you received as to the offer
+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
+    received the program in object code or executable form with such
+    an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it.  For an executable work, complete source
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+associated interface definition files, plus the scripts used to
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+operating system on which the executable runs, unless that component
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+
+If distribution of executable or object code is made by offering
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+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices.  Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission.  For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+          NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+         END OF TERMS AND CONDITIONS
+
+      How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/core/lib/Drupal/Component/VendorCleanup/README.txt b/core/lib/Drupal/Component/VendorCleanup/README.txt
new file mode 100644
index 0000000000..c4d51f12d3
--- /dev/null
+++ b/core/lib/Drupal/Component/VendorCleanup/README.txt
@@ -0,0 +1,40 @@
+The Drupal VendorCleanup Component
+
+Thanks for using this Drupal component.
+
+You can participate in its development on Drupal.org, through our issue system:
+https://www.drupal.org/project/issues/drupal
+
+You can get the full Drupal repo here:
+https://www.drupal.org/project/drupal/git-instructions
+
+You can browse the full Drupal repo here:
+http://cgit.drupalcode.org/drupal
+
+What does it do?
+
+Require this Composer plugin into your project:
+
+composer require drupal/core-vendor-cleanup
+
+Then perform a clean install or update:
+
+$ rm -rf vendor/
+$ composer install
+
+When you install or update, this plugin will look through each the package and
+remove directories it knows about.
+
+This is useful for removing test directories and other extraneous files from
+your project's vendor/ directory.
+
+You can see the default projects for this plugin in DefaultConfiguration.php.
+
+You can also set your own package/directory pairs in the root package's extra
+section, like this:
+
+"extra": {
+  "drupal-core-vendor-cleanup": {
+    "vendor/package": ["test", "documentation"]
+  }
+}
diff --git a/core/lib/Drupal/Component/VendorCleanup/TESTING.txt b/core/lib/Drupal/Component/VendorCleanup/TESTING.txt
new file mode 100644
index 0000000000..125d9fd8a3
--- /dev/null
+++ b/core/lib/Drupal/Component/VendorCleanup/TESTING.txt
@@ -0,0 +1,18 @@
+HOW-TO: Test this Drupal component
+
+In order to test this component, you'll need to get the entire Drupal repo and
+run the tests there.
+
+You'll find the tests under core/tests/Drupal/Tests/Component.
+
+You can get the full Drupal repo here:
+https://www.drupal.org/project/drupal/git-instructions
+
+You can find more information about running PHPUnit tests with Drupal here:
+https://www.drupal.org/node/2116263
+
+Each component in the Drupal\Component namespace has its own annotated test
+group. You can use this group to run only the tests for this component. Like
+this:
+
+$ ./vendor/bin/phpunit -c core --group Annotation
diff --git a/core/lib/Drupal/Component/VendorCleanup/VendorCleanupPlugin.php b/core/lib/Drupal/Component/VendorCleanup/VendorCleanupPlugin.php
new file mode 100644
index 0000000000..d5855c4258
--- /dev/null
+++ b/core/lib/Drupal/Component/VendorCleanup/VendorCleanupPlugin.php
@@ -0,0 +1,145 @@
+<?php
+
+namespace Drupal\Component\VendorCleanup;
+
+use Composer\Composer;
+use Composer\EventDispatcher\EventSubscriberInterface;
+use Composer\Installer\PackageEvent;
+use Composer\IO\IOInterface;
+use Composer\Package\CompletePackageInterface;
+use Composer\Plugin\PluginInterface;
+use Composer\Script\ScriptEvents;
+
+class VendorCleanupPlugin implements PluginInterface, EventSubscriberInterface {
+
+  /**
+   * Composer object.
+   *
+   * @var \Composer\Composer
+   */
+  protected $composer;
+
+  /**
+   * IO object.
+   *
+   * @var \Composer\IO\IOInterface
+   */
+  protected $io;
+
+  /**
+   * Configuration.
+   *
+   * @var \Drupal\Component\VendorCleanup\Config
+   */
+  protected $config;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function activate(Composer $composer, IOInterface $io) {
+    $this->composer = $composer;
+    $this->io = $io;
+
+    // Set up configuration.
+    $this->config = new Config($this->composer->getPackage());
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents() {
+    return [
+      ScriptEvents::POST_PACKAGE_INSTALL => 'onPostPackageInstall',
+      ScriptEvents::POST_PACKAGE_UPDATE => 'onPostPackageUpdate',
+    ];
+  }
+
+  /**
+   * POST_PACKAGE_INSTALL event handler.
+   *
+   * @param \Composer\Installer\PackageEvent $event
+   */
+  public function onPostPackageInstall(PackageEvent $event) {
+    /** @var \Composer\Package\CompletePackage $package */
+    $package = $event->getOperation()->getPackage();
+    $this->cleanPackage($this->composer->getConfig()->get('vendor-dir'), $package);
+  }
+
+  /**
+   * POST_PACKAGE_UPDATE event handler.
+   *
+   * @param \Composer\Installer\PackageEvent $event
+   */
+  public function onPostPackageUpdate(PackageEvent $event) {
+    /** @var \Composer\Package\CompletePackage $package */
+    $package = $event->getOperation()->getTargetPackage();
+    $this->cleanPackage($this->composer->getConfig()->get('vendor-dir'), $package);
+  }
+
+  /**
+   * Clean out the package.
+   *
+   * @param \Composer\Package\CompletePackageInterface $package
+   */
+  public function cleanPackage($vendor_dir, CompletePackageInterface $package) {
+    $package_name = $package->getName();
+    $paths_for_package = $this->config->getPathsForPackage($package_name);
+    if ($paths_for_package) {
+      $package_dir = $vendor_dir . '/' . $package_name;
+      if (is_dir($package_dir)) {
+        $this->io->write(sprintf("    Package cleanup for <comment>%s</comment>", $package_name), TRUE, IOInterface::VERBOSE);
+        foreach ($paths_for_package as $cleanup_item) {
+          $cleanup_path = $package_dir . '/' . $cleanup_item;
+          if (is_dir($cleanup_path)) {
+            if ($this->deleteRecursive($cleanup_path)) {
+              $this->io->write(sprintf("      <info>Removing directory '%s'</info>", $cleanup_item), TRUE, IOInterface::VERY_VERBOSE);
+            }
+            else {
+              // Always display a message if this fails as it means something
+              // has gone wrong. Therefore the message has to include the
+              // package name as the first informational message might not
+              // exist.
+              $this->io->write(sprintf("      <error>Failure removing directory '%s'</error> in package <comment>%s</comment>.", $cleanup_item, $package_name), TRUE, IOInterface::NORMAL);
+            }
+          }
+          else {
+            // If the package has changed or the --prefer-dist version does not
+            // include the directory. This is not an error.
+            $this->io->write(sprintf("      Directory '%s' does not exist.", $cleanup_path), TRUE, IOInterface::VERBOSE);
+          }
+        }
+        $this->io->write('', TRUE, IOInterface::VERBOSE);
+      }
+    }
+  }
+
+  /**
+   * Helper method to remove directories and the files they contain.
+   *
+   * @param string $path
+   *   The directory or file to remove. It must exist.
+   *
+   * @return bool
+   *   TRUE on success or FALSE on failure.
+   *
+   * @todo Make this part of the Filesystem or Utility component.
+   */
+  protected function deleteRecursive($path) {
+    if (is_file($path) || is_link($path)) {
+      return unlink($path);
+    }
+    $success = TRUE;
+    $dir = dir($path);
+    while (($entry = $dir->read()) !== FALSE) {
+      if ($entry == '.' || $entry == '..') {
+        continue;
+      }
+      $entry_path = $path . '/' . $entry;
+      $success = $this->deleteRecursive($entry_path) && $success;
+    }
+    $dir->close();
+
+    return rmdir($path) && $success;
+  }
+
+}
diff --git a/core/lib/Drupal/Component/VendorCleanup/composer.json b/core/lib/Drupal/Component/VendorCleanup/composer.json
new file mode 100644
index 0000000000..bdff5de260
--- /dev/null
+++ b/core/lib/Drupal/Component/VendorCleanup/composer.json
@@ -0,0 +1,18 @@
+{
+  "name": "drupal/core-vendor-cleanup",
+  "description": "Removes directories from the vendor directory.",
+  "keywords": ["drupal"],
+  "homepage": "https://www.drupal.org/project/drupal",
+  "license": "GPL-2.0-or-later",
+  "type": "composer-plugin",
+  "extra": {
+    "class": "Drupal\\Component\\VendorCleanup\\VendorCleanupPlugin"
+  },
+  "require": {
+    "php": ">=7.0.8",
+    "composer-plugin-api": "^1.1"
+  },
+  "autoload": {
+    "classmap": [""]
+  }
+}
diff --git a/core/tests/Drupal/Tests/Component/VendorCleanup/ConfigTest.php b/core/tests/Drupal/Tests/Component/VendorCleanup/ConfigTest.php
new file mode 100644
index 0000000000..ea3db03781
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/VendorCleanup/ConfigTest.php
@@ -0,0 +1,86 @@
+<?php
+
+namespace Drupal\Tests\Component\VendorCleanup;
+
+use Composer\Package\RootPackageInterface;
+use Drupal\Component\VendorCleanup\Config;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @coversDefaultClass Drupal\Component\VendorCleanup\Config
+ * @group VendorCleanup
+ */
+class ConfigTest extends TestCase {
+
+  /**
+   * @covers ::getPathsForPackage
+   */
+  public function testGetPathsForPackageMixedCase() {
+    $config = $this->getMockBuilder(Config::class)
+      ->setMethods(['getPluginConfig'])
+      ->disableOriginalConstructor()
+      ->getMock();
+
+    $config->expects($this->once())
+      ->method('getPluginConfig')
+      ->willReturn(['PackAge' => ['path']]);
+
+    $this->assertSame(['path'], $config->getPathsForPackage('pACKage'));
+  }
+
+  /**
+   * @covers ::getPluginConfig
+   */
+  public function testNoRootMergeConfig() {
+    // Root package has no extra field.
+    $root = $this->getMockBuilder(RootPackageInterface::class)
+      ->setMethods(['getExtra'])
+      ->getMockForAbstractClass();
+    $root->expects($this->once())
+      ->method('getExtra')
+      ->willReturn([]);
+
+    $config = new Config($root);
+
+    $ref_default = new \ReflectionProperty($config, 'defaultConfig');
+    $ref_default->setAccessible(TRUE);
+
+    $ref_plugin_config = new \ReflectionMethod($config, 'getPluginConfig');
+    $ref_plugin_config->setAccessible(TRUE);
+
+    $this->assertEquals(
+      $ref_default->getValue($config), $ref_plugin_config->invoke($config)
+    );
+  }
+
+  /**
+   * @covers ::getPluginConfig
+   */
+  public function testRootMergeConfig() {
+    // Root package has configuration in extra.
+    $root = $this->getMockBuilder(RootPackageInterface::class)
+      ->setMethods(['getExtra'])
+      ->getMockForAbstractClass();
+    $root->expects($this->once())
+      ->method('getExtra')
+      ->willReturn([
+        'drupal-core-vendor-cleanup' => [
+          'isa/string' => 'test_dir',
+          'an/array' => ['test_dir', 'doc_dir'],
+        ]
+      ]);
+
+    $config = new Config($root);
+
+    $ref_plugin_config = new \ReflectionMethod($config, 'getPluginConfig');
+    $ref_plugin_config->setAccessible(TRUE);
+
+    $plugin_config = $ref_plugin_config->invoke($config);
+
+    $this->assertArraySubset([
+      'isa/string' => ['test_dir'],
+      'an/array' => ['test_dir', 'doc_dir'],
+    ], $plugin_config);
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Component/VendorCleanup/VendorCleanupPluginTest.php b/core/tests/Drupal/Tests/Component/VendorCleanup/VendorCleanupPluginTest.php
new file mode 100644
index 0000000000..886e92124d
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/VendorCleanup/VendorCleanupPluginTest.php
@@ -0,0 +1,68 @@
+<?php
+
+namespace Drupal\Tests\Component\VendorCleanup;
+
+use Composer\IO\IOInterface;
+use Composer\Package\CompletePackageInterface;
+use Drupal\Component\VendorCleanup\Config;
+use Drupal\Component\VendorCleanup\VendorCleanupPlugin;
+use org\bovigo\vfs\vfsStream;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @coversDefaultClass Drupal\Component\VendorCleanup\VendorCleanupPlugin
+ * @group VendorCleanup
+ */
+class VendorCleanupPluginTest extends TestCase {
+
+  public function setUp() {
+    parent::setUp();
+    vfsStream::setup('vendor', NULL, [
+      'drupal' => [
+        'package' => [
+          'tests' => [
+            'SomeTest.php' => '<?php',
+          ],
+        ],
+      ],
+    ]);
+  }
+
+  /**
+   * @covers ::cleanPackage
+   */
+  public function testCleanPackage() {
+    $package = $this->getMockBuilder(CompletePackageInterface::class)
+      ->setMethods(['getName'])
+      ->disableOriginalConstructor()
+      ->getMockForAbstractClass();
+    $package->expects($this->once())
+      ->method('getName')
+      ->willReturn('drupal/package');
+
+    $config = $this->getMockBuilder(Config::class)
+      ->setMethods(['getPathsForPackage'])
+      ->disableOriginalConstructor()
+      ->getMock();
+    $config->expects($this->once())
+      ->method('getPathsForPackage')
+      ->willReturn(['tests']);
+
+    $plugin = new VendorCleanupPlugin();
+    $ref_config = new \ReflectionProperty($plugin, 'config');
+    $ref_config->setAccessible(TRUE);
+    $ref_config->setValue($plugin, $config);
+
+    $io = $this->prophesize(IOInterface::class);
+    $ref_io = new \ReflectionProperty($plugin, 'io');
+    $ref_io->setAccessible(TRUE);
+    $ref_io->setValue($plugin, $io->reveal());
+
+    $this->assertFileExists(vfsStream::url('vendor/drupal/package/tests/SomeTest.php'));
+
+    $plugin->cleanPackage(vfsStream::url('vendor'), $package);
+
+    $this->assertFileNotExists(vfsStream::url('vendor/drupal/package/tests'));
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/ComposerIntegrationTest.php b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
index 4bed30bcc9..1050641a94 100644
--- a/core/tests/Drupal/Tests/ComposerIntegrationTest.php
+++ b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
@@ -63,6 +63,7 @@ protected function getPaths() {
       $this->root . '/core/lib/Drupal/Component/Transliteration',
       $this->root . '/core/lib/Drupal/Component/Utility',
       $this->root . '/core/lib/Drupal/Component/Uuid',
+      $this->root . '/core/lib/Drupal/Component/VendorCleanup',
       $this->root . '/core/lib/Drupal/Component/Version',
     ];
   }