diff --git a/.gitignore b/.gitignore
index 9bbe0e7..6a2abd2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,11 @@
 # libraries lock file
 /installed-libraries.json
+# ide folders
+/.idea
 # composer artifacts
-/vendor/
+/.phpunit.result.cache
+/composer.lock
+/composer.phar
+/phpunit.xml
+/reports
+/vendor
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..4587401
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,19 @@
+1.2.0 / 2020-07-14
+========================
+
+* Quality of life improvements such as an alternative configuration
+definition for supporting:
+    * Different file extensions.
+    * SHA1 checksum verification.
+    * Removing example/demo/test files from the libraries (see [PSA-2011-002](https://www.drupal.org/node/1189632)).
+* Ability to pull in library dependencies declared in subpackages through the
+`drupal-libraries-dependencies` extra option.
+* Basic unit tests.
+
+1.0.1 / 2018-01-25 
+========================
+* Relax composer-installers version requirement.
+
+1.0.0 / 2018-01-25 
+========================
+* Initial MVP plugin.
diff --git a/README.md b/README.md
index 2c8ee61..ab88e13 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ external dependencies for a Drupal site in a single place: the `composer.json` f
 1. Add _Drupal Libraries Installer_ to your Drupal site project:
 
     ```sh
-    composer require balbuf/drupal-libraries-installer
+    composer require zodiacmedia/drupal-libraries-installer
     ```
 
 1. Add libraries to your `composer.json` file via the `drupal-libraries` property
diff --git a/composer.json b/composer.json
index 9fe3cb9..5df181a 100644
--- a/composer.json
+++ b/composer.json
@@ -1,5 +1,5 @@
 {
-    "name": "balbuf/drupal-libraries-installer",
+    "name": "zodiacmedia/drupal-libraries-installer",
     "description": "Install Drupal libraries via a simple listing in your composer.json file",
     "type": "composer-plugin",
     "license": "MIT",
@@ -7,19 +7,42 @@
         {
             "name": "Stephen Beemsterboer",
             "homepage": "https://github.com/balbuf"
+        },
+        {
+            "name": "codebymikey",
+            "homepage": "https://www.drupal.org/u/codebymikey"
         }
     ],
     "support": {
-        "issues": "https://github.com/balbuf/drupal-libraries-installer/issues"
+        "issues": "https://github.com/zodiacmedia/drupal-libraries-installer/issues"
     },
     "autoload": {
-        "psr-4": {"BalBuf\\DrupalLibrariesInstaller\\": "src/"}
+        "psr-4": {
+            "Zodiacmedia\\DrupalLibrariesInstaller\\": "src/"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Zodiacmedia\\DrupalLibrariesInstaller\\": "tests"
+        }
     },
     "extra": {
-        "class": "BalBuf\\DrupalLibrariesInstaller\\Plugin"
+        "class": "Zodiacmedia\\DrupalLibrariesInstaller\\Plugin"
+    },
+    "scripts": {
+        "phpunit": "phpunit",
+        "coverage": "phpunit --coverage-text",
+        "coverage:report": "phpunit --log-junit=reports/unitreport.xml --coverage-text --coverage-html=reports/coverage --coverage-clover=reports/coverage.xml"
     },
     "require": {
         "composer-plugin-api": "^1.0",
-        "composer/installers": "^1.1"
+        "composer/installers": "^1.1",
+        "php": ">=7.2.0"
+    },
+    "require-dev": {
+        "composer/composer": "^1.10",
+        "mikey179/vfsstream": "^1.6",
+        "phpunit/phpunit": "^8.5",
+        "ext-json": "*"
     }
 }
diff --git a/composer.lock b/composer.lock
deleted file mode 100644
index 50cf0c1..0000000
--- a/composer.lock
+++ /dev/null
@@ -1,138 +0,0 @@
-{
-    "_readme": [
-        "This file locks the dependencies of your project to a known state",
-        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
-        "This file is @generated automatically"
-    ],
-    "content-hash": "0d5407f7f7233a1bd639fd22d5542230",
-    "packages": [
-        {
-            "name": "composer/installers",
-            "version": "v1.5.0",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/composer/installers.git",
-                "reference": "049797d727261bf27f2690430d935067710049c2"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/composer/installers/zipball/049797d727261bf27f2690430d935067710049c2",
-                "reference": "049797d727261bf27f2690430d935067710049c2",
-                "shasum": ""
-            },
-            "require": {
-                "composer-plugin-api": "^1.0"
-            },
-            "replace": {
-                "roundcube/plugin-installer": "*",
-                "shama/baton": "*"
-            },
-            "require-dev": {
-                "composer/composer": "1.0.*@dev",
-                "phpunit/phpunit": "^4.8.36"
-            },
-            "type": "composer-plugin",
-            "extra": {
-                "class": "Composer\\Installers\\Plugin",
-                "branch-alias": {
-                    "dev-master": "1.0-dev"
-                }
-            },
-            "autoload": {
-                "psr-4": {
-                    "Composer\\Installers\\": "src/Composer/Installers"
-                }
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Kyle Robinson Young",
-                    "email": "kyle@dontkry.com",
-                    "homepage": "https://github.com/shama"
-                }
-            ],
-            "description": "A multi-framework Composer library installer",
-            "homepage": "https://composer.github.io/installers/",
-            "keywords": [
-                "Craft",
-                "Dolibarr",
-                "Eliasis",
-                "Hurad",
-                "ImageCMS",
-                "Kanboard",
-                "Lan Management System",
-                "MODX Evo",
-                "Mautic",
-                "Maya",
-                "OXID",
-                "Plentymarkets",
-                "Porto",
-                "RadPHP",
-                "SMF",
-                "Thelia",
-                "WolfCMS",
-                "agl",
-                "aimeos",
-                "annotatecms",
-                "attogram",
-                "bitrix",
-                "cakephp",
-                "chef",
-                "cockpit",
-                "codeigniter",
-                "concrete5",
-                "croogo",
-                "dokuwiki",
-                "drupal",
-                "eZ Platform",
-                "elgg",
-                "expressionengine",
-                "fuelphp",
-                "grav",
-                "installer",
-                "itop",
-                "joomla",
-                "kohana",
-                "laravel",
-                "lavalite",
-                "lithium",
-                "magento",
-                "majima",
-                "mako",
-                "mediawiki",
-                "modulework",
-                "modx",
-                "moodle",
-                "osclass",
-                "phpbb",
-                "piwik",
-                "ppi",
-                "puppet",
-                "pxcms",
-                "reindex",
-                "roundcube",
-                "shopware",
-                "silverstripe",
-                "sydes",
-                "symfony",
-                "typo3",
-                "wordpress",
-                "yawik",
-                "zend",
-                "zikula"
-            ],
-            "time": "2017-12-29T09:13:20+00:00"
-        }
-    ],
-    "packages-dev": [],
-    "aliases": [],
-    "minimum-stability": "stable",
-    "stability-flags": [],
-    "prefer-stable": false,
-    "prefer-lowest": false,
-    "platform": [],
-    "platform-dev": []
-}
diff --git a/example/dependency/README.md b/example/dependency/README.md
new file mode 100644
index 0000000..2928ac0
--- /dev/null
+++ b/example/dependency/README.md
@@ -0,0 +1,5 @@
+# Demo dependency package.
+
+Demo dependency package includes a `moment` library version 2.0.0 which will 
+not be installed because it was already declared in the root project's 
+composer.json.
diff --git a/example/dependency/composer.json b/example/dependency/composer.json
new file mode 100644
index 0000000..3c41957
--- /dev/null
+++ b/example/dependency/composer.json
@@ -0,0 +1,17 @@
+{
+    "name": "zodiacmedia/drupal-libraries-installer-demo-dependency",
+    "type": "project",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "codebymikey",
+            "homepage": "https://www.drupal.org/u/codebymikey"
+        }
+    ],
+    "extra": {
+        "drupal-libraries": {
+            "dependency@flexslider": "https://github.com/woocommerce/FlexSlider/archive/2.6.4.zip",
+            "moment": "https://registry.npmjs.org/moment/-/moment-2.0.0.tgz"
+        }
+    }
+}
diff --git a/example/project/.gitignore b/example/project/.gitignore
new file mode 100644
index 0000000..25f3ea5
--- /dev/null
+++ b/example/project/.gitignore
@@ -0,0 +1,3 @@
+/composer.lock
+/vendor
+/web
diff --git a/example/project/README.md b/example/project/README.md
new file mode 100644
index 0000000..df92d3c
--- /dev/null
+++ b/example/project/README.md
@@ -0,0 +1,3 @@
+# Demo root project
+
+Demo root project integrating with Drupal libraries installer.
diff --git a/example/project/composer.json b/example/project/composer.json
new file mode 100644
index 0000000..66a9831
--- /dev/null
+++ b/example/project/composer.json
@@ -0,0 +1,75 @@
+{
+    "name": "zodiacmedia/drupal-libraries-installer-demo-project",
+    "description": "Demo project using the installer.",
+    "type": "project",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "codebymikey",
+            "homepage": "https://www.drupal.org/u/codebymikey"
+        }
+    ],
+    "repositories": {
+        "drupal-libraries-installer": {
+            "type": "vcs",
+            "url": "../.."
+        },
+        "drupal-libraries-installer-demo-dependency": {
+            "type": "path",
+            "url": "../dependency/",
+            "options": {
+                "symlink": true
+            }
+        }
+    },
+    "require": {
+        "zodiacmedia/drupal-libraries-installer": "*@dev",
+        "zodiacmedia/drupal-libraries-installer-demo-dependency": "*@dev"
+    },
+    "config": {
+        "preferred-install": "source",
+        "classmap-authoritative": true,
+        "prepend-autoloader": false,
+        "optimize-autoloader": true
+    },
+    "extra": {
+        "installer-paths": {
+            "web/libraries/{$name}/": [
+                "type:drupal-library"
+            ]
+        },
+        "drupal-libraries-dependencies": [
+            "zodiacmedia/drupal-libraries-installer-demo-dependency"
+        ],
+        "drupal-libraries": {
+            "simple-color": "https://github.com/recurser/jquery-simple-color/archive/v1.2.2.zip",
+            "chosen": {
+                "url": "https://github.com/harvesthq/chosen/releases/download/v1.8.2/chosen_v1.8.2.zip",
+                "version": "1.8.2"
+            },
+            "flexslider": {
+                "url": "https://github.com/woocommerce/FlexSlider/archive/2.6.4.zip",
+                "version": "2.6.4",
+                "type": "zip",
+                "ignore": [
+                    "bower_components",
+                    "demo",
+                    "node_modules"
+                ]
+            },
+            "moment": {
+                "url": "https://registry.npmjs.org/moment/-/moment-2.25.0.tgz",
+                "shasum": "e961ab9a5848a1cf2c52b1af4e6c82a8401e7fe9"
+            },
+            "select2": {
+                "url": "https://github.com/select2/select2/archive/4.0.13.zip",
+                "ignore": [
+                    ".*",
+                    "*.{md}",
+                    "Gruntfile.js",
+                    "{docs,src,tests}"
+                ]
+            }
+        }
+    }
+}
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
new file mode 100644
index 0000000..74cbacf
--- /dev/null
+++ b/phpunit.xml.dist
@@ -0,0 +1,15 @@
+<phpunit colors="true"
+         beStrictAboutTestsThatDoNotTestAnything="true"
+         beStrictAboutOutputDuringTests="true"
+         beStrictAboutChangesToGlobalState="true">
+    <testsuites>
+        <testsuite name="Tests">
+            <directory>./tests</directory>
+        </testsuite>
+    </testsuites>
+    <filter>
+        <whitelist addUncoveredFilesFromWhitelist="true">
+            <directory suffix=".php">./src</directory>
+        </whitelist>
+    </filter>
+</phpunit>
diff --git a/src/Plugin.php b/src/Plugin.php
index bf827e3..110f009 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -1,20 +1,24 @@
 <?php
 
-namespace BalBuf\DrupalLibrariesInstaller;
+namespace Zodiacmedia\DrupalLibrariesInstaller;
 
 use Composer\Composer;
+use Composer\EventDispatcher\EventSubscriberInterface;
 use Composer\IO\IOInterface;
 use Composer\Json\JsonFile;
 use Composer\Package\CompletePackage;
+use Composer\Package\Package;
+use Composer\Package\PackageInterface;
 use Composer\Plugin\PluginInterface;
-use Composer\EventDispatcher\EventSubscriberInterface;
 use Composer\Script\Event;
 use Composer\Script\ScriptEvents;
-use Composer\Package\Package;
 use Composer\Util\Filesystem;
 use Symfony\Component\Finder\Finder;
 use Symfony\Component\Finder\Glob;
 
+/**
+ * The Drupal libraries installer plugin.
+ */
 class Plugin implements PluginInterface, EventSubscriberInterface {
 
   /**
@@ -27,41 +31,58 @@ class Plugin implements PluginInterface, EventSubscriberInterface {
   /**
    * The composer package name.
    */
-  const PACKAGE_NAME = 'balbuf/drupal-libraries-installer';
+  const PACKAGE_NAME = 'zodiacmedia/drupal-libraries-installer';
 
   /**
-   * @var Composer $composer
+   * The composer instance.
+   *
+   * @var \Composer\Composer
    */
   protected $composer;
 
   /**
-   * @var IOInterface $io
+   * The input/output controller instance.
+   *
+   * @var \Composer\IO\IOInterface
    */
   protected $io;
 
   /**
+   * The download manager instance.
+   *
    * @var \Composer\Downloader\DownloadManager
    */
   protected $downloadManager;
 
   /**
+   * The installation manager instance.
+   *
    * @var \Composer\Installer\InstallationManager
    */
   protected $installationManager;
 
   /**
+   * The file system utility instance.
+   *
    * @var \Composer\Util\Filesystem
    */
   protected $fileSystem;
 
   /**
    * Called when the composer plugin is activated.
+   *
+   * @param \Composer\Composer $composer
+   *   The composer instance.
+   * @param \Composer\IO\IOInterface $io
+   *   The input/output controller.
+   * @param \Composer\Util\Filesystem|null $filesystem
+   *   The filesystem utility helper.
    */
-  public function activate(Composer $composer, IOInterface $io) {
+  public function activate(Composer $composer, IOInterface $io, Filesystem $filesystem = NULL) {
     $this->composer = $composer;
 
     $this->io = $io;
-    $this->fileSystem = new Filesystem();
+    $this->fileSystem = $filesystem ?? new Filesystem();
     $this->downloadManager = $composer->getDownloadManager();
     $this->installationManager = $composer->getInstallationManager();
   }
@@ -79,7 +100,8 @@ public static function getSubscribedEvents() {
   /**
    * Upon running composer install or update, install the drupal libraries.
    *
-   * @param Event $event  install/update event
+   * @param \Composer\Script\Event $event
+   *   The composer install/update event.
    *
    * @throws \Exception
    */
@@ -128,8 +150,8 @@ public function install(Event $event) {
     }
 
     // Remove unused libraries from disk before attempting to download new ones.
-    // Avoids the edge-case where the removed folder happens to be the same as the one where the new one is being
-    // installed to.
+    // Avoids the edge-case where the removed folder happens to be the same as
+    // the one where a new package dependency is being installed to.
     $removed_libraries = array_diff_key($applied_drupal_libraries, $processed_drupal_libraries);
     if ($removed_libraries) {
       $this->removeUnusedLibraries($removed_libraries);
@@ -153,38 +175,40 @@ public function install(Event $event) {
   /**
    * Drupal library processor.
    *
-   * Inspired by https://github.com/civicrm/composer-downloads-plugin
+   * Inspired by https://github.com/civicrm/composer-downloads-plugin.
    *
    * @param array $processed_drupal_libraries
+   *   The currently processed drupal libraries.
    * @param array $drupal_libraries
-   *   Applied drupal libraries.
+   *   The currently installed drupal libraries.
    * @param \Composer\Package\PackageInterface $package
+   *   The package instance.
    *
    * @return array
    *   The processed packages.
    */
-  protected function processPackage($processed_drupal_libraries, $drupal_libraries, $package) {
+  protected function processPackage(array $processed_drupal_libraries, array $drupal_libraries, PackageInterface $package) {
     $extra = $package->getExtra();
 
     if (empty($extra['drupal-libraries']) || !is_array($extra['drupal-libraries'])) {
       return $processed_drupal_libraries;
     }
 
-    // Install each library
+    // Install each library.
     foreach ($extra['drupal-libraries'] as $library => $library_definition) {
       $ignore_patterns = [];
       $sha1checksum = NULL;
       if (is_string($library_definition)) {
         // Simple format.
         $url = $library_definition;
-        list($version, $distribution_type) = $this->guessDefaultsFromUrl($url);
+        [$version, $distribution_type] = $this->guessDefaultsFromUrl($url);
       }
       else {
         if (empty($library_definition['url'])) {
           throw new \LogicException("The drupal-library '$library' does not contain a valid URL.");
         }
         $url = $library_definition['url'];
-        list($version, $distribution_type) = $this->guessDefaultsFromUrl($url);
+        [$version, $distribution_type] = $this->guessDefaultsFromUrl($url);
         $version = $library_definition['version'] ?? $version;
         $distribution_type = $library_definition['type'] ?? $distribution_type;
         $ignore_patterns = $library_definition['ignore'] ?? $ignore_patterns;
@@ -192,8 +216,9 @@ protected function processPackage($processed_drupal_libraries, $drupal_libraries
       }
 
       if (isset($processed_drupal_libraries[$library])) {
-        // Only the first declaration of the library is ever used. This ensures that the root package always
-        // acts as the source of truth over what version of a library is installed.
+        // Only the first declaration of the library is ever used. This ensures
+        // that the root package always acts as the source of truth over what
+        // version of a library is installed.
         $old_definition = $processed_drupal_libraries[$library];
         if ($this->io->isDebug()) {
           $this->io->write(
@@ -207,7 +232,8 @@ protected function processPackage($processed_drupal_libraries, $drupal_libraries
         }
       }
       else {
-        // Track installed libraries in the package info in installed-libraries.json
+        // Track installed libraries in the package info in
+        // installed-libraries.json.
         $applied_library = [
           'version' => $version,
           'url' => $url,
@@ -230,8 +256,9 @@ protected function processPackage($processed_drupal_libraries, $drupal_libraries
    * Remove old unused libraries from disk.
    *
    * @param array $old_libraries
+   *   The old libraries to remove from disk.
    */
-  protected function removeUnusedLibraries($old_libraries) {
+  protected function removeUnusedLibraries(array $old_libraries) {
     foreach ($old_libraries as $library_name => $library_definition) {
       $library_package = $this->getLibraryPackage($library_name, $library_definition);
 
@@ -247,8 +274,10 @@ protected function removeUnusedLibraries($old_libraries) {
    *
    * @param array $processed_libraries
    *   The processed libraries.
+   * @param array $applied_drupal_libraries
+   *   The currently installed libraries.
    */
-  protected function downloadLibraries($processed_libraries, $applied_drupal_libraries) {
+  protected function downloadLibraries(array $processed_libraries, array $applied_drupal_libraries) {
     foreach ($processed_libraries as $library_name => $processed_library) {
       $library_package = $this->getLibraryPackage($library_name, $processed_library);
 
@@ -280,7 +309,7 @@ protected function downloadLibraries($processed_libraries, $applied_drupal_libra
    * @param array $ignore_patterns
    *   File patterns to ignore.
    */
-  protected function downloadPackage(Package $library_package, $install_path, $ignore_patterns) {
+  protected function downloadPackage(Package $library_package, $install_path, array $ignore_patterns) {
     // Let composer download and unpack the library for us!
     $this->downloadManager->download($library_package, $install_path);
 
@@ -328,12 +357,15 @@ function ($file) use ($patterns) {
   /**
    * Get a drupal-library package object from its definition.
    *
-   * @param $library_name
-   * @param $library_definition
+   * @param string $library_name
+   *   The library name.
+   * @param array $library_definition
+   *   The library definition.
    *
    * @return \Composer\Package\Package
+   *   The pseudo-package for the library.
    */
-  protected function getLibraryPackage($library_name, $library_definition) {
+  protected function getLibraryPackage($library_name, array $library_definition) {
     $library_package_name = 'drupal-library/' . $library_name;
     $library_package = new Package(
       $library_package_name, $library_definition['version'], $library_definition['version']
@@ -380,10 +412,11 @@ protected function guessDefaultsFromUrl($url) {
    * Get the current installed-libraries json file path.
    *
    * @return string
+   *   The installed libraries json lock file path.
    */
-  protected function getInstalledJsonPath() {
+  public function getInstalledJsonPath() {
     // Alternative approach.
-    // $installed_json_file = __DIR__ . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . 'installed-libraries.json';
+    /*$installed_json_file = __DIR__ . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . 'installed-libraries.json';*/
 
     /** @var \Composer\Package\CompletePackage $installer_library_package */
     $installer_library_package = $this->composer->getRepositoryManager()->getLocalRepository()->findPackage(
diff --git a/tests/PluginTest.php b/tests/PluginTest.php
new file mode 100644
index 0000000..a85c224
--- /dev/null
+++ b/tests/PluginTest.php
@@ -0,0 +1,600 @@
+<?php
+
+namespace Zodiacmedia\DrupalLibrariesInstaller;
+
+use Composer\Composer;
+use Composer\Downloader\DownloadManager;
+use Composer\Installer\InstallationManager;
+use Composer\IO\IOInterface;
+use Composer\Package\Link;
+use Composer\Package\Package;
+use Composer\Package\RootPackage;
+use Composer\Repository\RepositoryManager;
+use Composer\Repository\WritableRepositoryInterface;
+use Composer\Script\Event;
+use Composer\Script\ScriptEvents;
+use Composer\Util\Filesystem;
+use org\bovigo\vfs\vfsStream;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \Zodiacmedia\DrupalLibrariesInstaller\Plugin
+ *
+ * The plugin test case.
+ *
+ * @todo Achieve 100% code coverage.
+ */
+class PluginTest extends TestCase {
+
+  /**
+   * The root directory.
+   *
+   * @var \org\bovigo\vfs\vfsStreamDirectory
+   */
+  private $rootDirectory;
+
+  /**
+   * The composer instance.
+   *
+   * @var \Composer\Composer
+   */
+  protected $composer;
+
+  /**
+   * The download manager instance.
+   *
+   * @var \Composer\Downloader\DownloadManager
+   */
+  protected $downloadManager;
+
+  /**
+   * The installation manager instance.
+   *
+   * @var \Composer\Installer\InstallationManager
+   */
+  protected $installationManager;
+
+  /**
+   * The file system instance.
+   *
+   * @var \Composer\Util\Filesystem
+   */
+  protected $fileSystem;
+
+  /**
+   * The input-output interface.
+   *
+   * @var \Composer\IO\IOInterface
+   */
+  protected $io;
+
+  /**
+   * The plugin interface fixture.
+   *
+   * @var \Zodiacmedia\DrupalLibrariesInstaller\Plugin
+   */
+  protected $fixture;
+
+  /**
+   * The virtual installed libraries json lock file.
+   *
+   * @var string
+   */
+  protected $installedLibrariesJsonFile;
+
+  /**
+   * The current fixture directory.
+   *
+   * @var string
+   */
+  protected $fixtureDirectory;
+
+  /**
+   * Removed files.
+   *
+   * @var array
+   */
+  protected $removedFiles;
+
+  /**
+   * Downloaded files.
+   *
+   * @var array
+   */
+  protected $downloadedFiles;
+
+  /**
+   * The libraries directory.
+   *
+   * @var string
+   */
+  const LIBRARIES_DIRECTORY = 'temp-libraries';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->downloadedFiles = [];
+    $this->removedFiles = [];
+
+    $this->setupVirtualFilesystem();
+
+    $this->installationManager = $this->createMock(InstallationManager::class);
+    $this->installationManager
+      ->method('getInstallPath')
+      ->willReturnCallback([$this, 'getInstallPathCallback']);
+
+    $this->downloadManager = $this->createMock(DownloadManager::class);
+    $this->downloadManager->method('download')->willReturnCallback(
+      [$this, 'downloadManagerDownloadCallback']
+    );
+
+    // Create a partial mock, keeping the normalize functionality.
+    $this->fileSystem = $this->createPartialMock(Filesystem::class, ['remove']);
+    $this->fileSystem->method('remove')->willReturnCallback(
+      [$this, 'fileSystemRemoveCallback']
+    );
+
+    $this->composer = $this
+      ->createPartialMock(
+        Composer::class,
+        [
+          'getPackage',
+          'getInstallationManager',
+          'getDownloadManager',
+          'getRepositoryManager',
+        ]
+      );
+    $this->composer
+      ->method('getInstallationManager')
+      ->willReturn($this->installationManager);
+
+    $this->composer
+      ->method('getDownloadManager')
+      ->willReturn($this->downloadManager);
+
+    $repository_manager = $this->createMock(RepositoryManager::class);
+    $local_repository = $this->createMock(WritableRepositoryInterface::class);
+    $local_repository
+      ->method('getCanonicalPackages')
+      ->willReturnCallback([$this, 'getCanonicalPackagesCallback']);
+    $repository_manager
+      ->method('getLocalRepository')
+      ->willReturn($local_repository);
+
+    $this->composer
+      ->method('getRepositoryManager')
+      ->willReturn($repository_manager);
+
+    $this->io = $this->createMock(IOInterface::class);
+
+    $this->fixture = $this->getPluginMockInstance();
+  }
+
+  /**
+   * Callback for the FileSystem's remove method.
+   *
+   * @param string $file
+   *   The file/folder path.
+   */
+  public function fileSystemRemoveCallback($file) {
+    $this->removedFiles[] = $file;
+  }
+
+  /**
+   * Callback for the DownloadManager's download function.
+   */
+  public function downloadManagerDownloadCallback(Package $package, $file) {
+    $this->downloadedFiles[] = $file;
+  }
+
+  /**
+   * Normalize a libraries directory vfs file path for comparison.
+   *
+   * @param string $file
+   *   The file path.
+   *
+   * @return string
+   *   The normalized path.
+   */
+  protected function normalizeVfsFilePath(string $file) {
+    $path_prefix = $this->rootDirectory->getChild(static::LIBRARIES_DIRECTORY)->url() . '/';
+    $path_prefix_length = strlen($path_prefix);
+    if (substr($file, 0, $path_prefix_length) === $path_prefix) {
+      $file = substr($file, $path_prefix_length);
+    }
+
+    return $file;
+  }
+
+  /**
+   * Prepares the virtual file system.
+   */
+  protected function setupVirtualFilesystem() {
+    // Not all tests require this, but we want to ensure we never accidentally
+    // touch our real composer.json.
+    $project_dependencies = [
+      'vendor' => [
+        'zodiacmedia' => [
+          'drupal-libraries-installer' => [
+            // 'installed-libraries.json' => '{}',
+          ],
+          'drupal-libraries-test-dependency' => [
+            'composer.json' => /* @lang JSON */
+            <<<EOL
+{
+  "name": "zodiacmedia/drupal-libraries-test-dependency",
+  "extra": {
+    "drupal-libraries": {
+      "test-library-dependency": "https://example.com/test-library-dependency.zip",
+      "test-moment": {
+        "url": "https://registry.npmjs.org/moment/-/moment-2.25.0.tgz",
+        "shasum": "e961ab9a5848a1cf2c52b1af4e6c82a8401e7fe9",
+        "ignore": [
+          "*.md"
+        ]
+      }
+    }
+  }
+}
+EOL
+          ],
+        ],
+      ],
+    ];
+    // Create the project structure.
+    $this->rootDirectory = vfsStream::setup('root', NULL, $project_dependencies);
+
+    $this->installedLibrariesJsonFile = vfsStream::url(
+      $this->rootDirectory->path() . '/vendor/zodiacmedia/drupal-libraries-installer/installed-libraries.json'
+    );
+  }
+
+  /**
+   * Test to ensure the correct events are acted upon.
+   *
+   * @covers \Zodiacmedia\DrupalLibrariesInstaller\Plugin::getSubscribedEvents()
+   */
+  public function testGetSubscribedEvents() {
+    $this->assertEquals(
+      [
+        ScriptEvents::POST_INSTALL_CMD => 'install',
+        ScriptEvents::POST_UPDATE_CMD => 'install',
+      ],
+      Plugin::getSubscribedEvents()
+    );
+  }
+
+  /**
+   * Test various drupal libraries scenarios.
+   *
+   * @param string $fixture_name
+   *   The fixture directory name.
+   * @param array $expected_removed_files
+   *   The list of removed files.
+   * @param array $expected_downloaded_dirs
+   *   The list of downloaded package directories.
+   * @param bool $installed_libraries
+   *   Whether to read an initial installed libraries.
+   *
+   * @dataProvider drupalLibrariesDownloadProvider
+   *
+   * @throws \Exception
+   */
+  public function testDrupalLibrariesDownload(
+    $fixture_name,
+    array $expected_removed_files,
+    array $expected_downloaded_dirs,
+    $installed_libraries = FALSE
+  ) {
+    $this->fixtureDirectory = $this->fixtureDirectory($fixture_name);
+    $root_project = $this->rootFromJson("{$this->fixtureDirectory}/composer.json");
+
+    if ($installed_libraries) {
+      // Set the initial installed libraries content if any.
+      copy("{$this->fixtureDirectory}/installed-libraries.initial.json", $this->installedLibrariesJsonFile);
+    }
+
+    // Create the libraries structure.
+    $this->createLibrariesPackageStructures("{$this->fixtureDirectory}/libraries-structure.json");
+
+    $this->triggerPlugin($root_project, $this->fixtureDirectory);
+
+    $removed_files = array_map([$this, 'normalizeVfsFilePath'], $this->removedFiles);
+    $downloaded_files = array_map([$this, 'normalizeVfsFilePath'], $this->downloadedFiles);
+    $this->assertSame($expected_removed_files, $removed_files, 'Removed files');
+    $this->assertSame($expected_downloaded_dirs, $downloaded_files, 'Downloaded files');
+
+    // Compare the output JSON files.
+    $expected_installed_libraries_file = "{$this->fixtureDirectory}/installed-libraries.expected.json";
+    $this->assertFileExists($expected_installed_libraries_file);
+    $this->assertFileExists($this->installedLibrariesJsonFile);
+    $this->assertSame(
+      json_decode(file_get_contents($expected_installed_libraries_file), TRUE),
+      json_decode(file_get_contents($this->installedLibrariesJsonFile), TRUE),
+      'installed-libraries.json output'
+    );
+  }
+
+  /**
+   * Fixtures data provider.
+   */
+  public function drupalLibrariesDownloadProvider() {
+    return [
+      'download-and-ignore-library-files' => [
+        /*
+         * Given a root package with
+         *   a set of different drupal library definitions.
+         * When the plugin is run
+         * Then the libraries are installed and certain files matching specific
+         *   ignore patterns are removed.
+         */
+        'download-and-ignore-library-files',
+        [
+          'flexslider/bower_components',
+          'flexslider/demo',
+          'flexslider/node_modules',
+          'select2/.git',
+          'select2/.hidden_directory',
+          'select2/docs',
+          'select2/src',
+          'select2/tests',
+          'select2/.hidden.txt',
+          'select2/Gruntfile.js',
+          'select2/README.md',
+        ],
+        [
+          'flexslider',
+          'moment',
+          'select2',
+          'simple-color',
+        ],
+      ],
+      'specific-dependency-libraries-with-override' => [
+        /*
+         * Given a root package with
+         *   a drupal library override and a package dependency with a library
+         *   definition.
+         * When the plugin is run
+         * Then the libraries are installed and the override kept.
+         */
+        'specific-dependency-libraries-with-override',
+        [],
+        [
+          'test-moment',
+          'test-library-dependency',
+        ],
+      ],
+      'specific-dependency-libraries' => [
+        /*
+         * Given a root package with
+         *   a package dependency with a library definition.
+         * When the plugin is run
+         * Then the libraries are installed and ignore patterns applied.
+         */
+        'specific-dependency-libraries',
+        [
+          'test-moment/README.md',
+        ],
+        [
+          'test-library-dependency',
+          'test-moment',
+        ],
+      ],
+      'all-dependency-libraries' => [
+        /*
+         * Given a root package with
+         *   a wildcard package dependency library definition.
+         * When the plugin is run
+         * Then the dependency libraries are installed and their ignore
+         *    patterns applied.
+         */
+        'all-dependency-libraries',
+        [
+          'test-moment/README.md',
+        ],
+        [
+          'test-library-dependency',
+          'test-moment',
+        ],
+      ],
+      'existing-lock-file' => [
+        /*
+         * Given a project with an existing lock file with the library.
+         *   and the project already exists on disk.
+         * When the plugin is run
+         * Then nothing is installed/removed.
+         */
+        'existing-lock-file',
+        [],
+        [],
+        TRUE,
+      ],
+    ];
+  }
+
+  /**
+   * Returns the mock plugin fixture instance.
+   */
+  protected function getPluginMockInstance() {
+    /** @var \PHPUnit\Framework\MockObject\MockObject|\Zodiacmedia\DrupalLibrariesInstaller\Plugin $plugin */
+    $plugin = $this->createPartialMock(Plugin::class, ['getInstalledJsonPath']);
+    $plugin->method('getInstalledJsonPath')->willReturn(
+      $this->installedLibrariesJsonFile
+    );
+
+    return $plugin;
+  }
+
+  /**
+   * Trigger an installation of the specified plugin.
+   *
+   * @param \Composer\Package\RootPackage $package
+   *   The package instance.
+   * @param string $directory
+   *   Working directory for composer run.
+   *
+   * @throws \Exception
+   */
+  protected function triggerPlugin(RootPackage $package, $directory) {
+    chdir($directory);
+    // Return the current package.
+    $this->composer->method('getPackage')->willReturn($package);
+
+    // Activate the plugin.
+    $this->fixture->activate(
+      $this->composer,
+      $this->io,
+      $this->fileSystem
+    );
+
+    $event = new Event(
+      ScriptEvents::POST_INSTALL_CMD,
+      $this->composer,
+      $this->io,
+    // Dev mode.
+      FALSE,
+      [],
+      []
+    );
+    $this->fixture->install($event);
+  }
+
+  /**
+   * Returns a fixture directory.
+   *
+   * @param string $sub_directory
+   *   The subdirectory.
+   *
+   * @return string
+   *   The fixture directory.
+   */
+  protected function fixtureDirectory($sub_directory) {
+    return __DIR__ . "/fixtures/{$sub_directory}";
+  }
+
+  /**
+   * Returns the root package definition.
+   *
+   * @param string $file
+   *   The fixture composer.json.
+   *
+   * @return \PHPUnit\Framework\MockObject\MockObject|\Composer\Package\RootPackage
+   *   The root package prophecy instance.
+   */
+  protected function rootFromJson($file) {
+    $json = json_decode(file_get_contents($file), TRUE);
+    $data = array_merge(
+      [
+        'name' => 'drupal-libraries-installer-test/root-package',
+        'repositories' => [],
+        'require' => [],
+        'require-dev' => [],
+        'suggest' => [],
+        'extra' => [],
+      ],
+      $json
+    );
+
+    $root_name = $data['name'];
+
+    foreach (['require', 'require-dev'] as $config) {
+      foreach ($data[$config] as $dependency => $dependency_version) {
+        $link = $this->createMock(Link::class);
+        $link->method('getSource')->willReturn($root_name);
+        $link->method('getTarget')->willReturn($dependency);
+        $link->method('getPrettyConstraint')->willReturn($dependency_version);
+        $data[$config][$dependency] = $link;
+      }
+    }
+
+    $root_package = $this->createMock(RootPackage::class);
+    $root_package->method('getRequires')->willReturn($data['require']);
+    $root_package->method('getDevRequires')->willReturn($data['require-dev']);
+    $root_package->method('getRepositories')->willReturn($data['repositories']);
+    $root_package->method('getSuggests')->willReturn($data['suggest']);
+    $root_package->method('getName')->willReturn($root_name);
+    $root_package->expects($this->atLeastOnce())->method('getExtra')->willReturn($data['extra']);
+
+    return $root_package;
+  }
+
+  /**
+   * Returns the composer package directory path.
+   *
+   * It also declares a bunch of files for the globs to match.
+   *
+   * @param \Composer\Package\Package $package
+   *   The composer package.
+   *
+   * @return string
+   *   The install path.
+   */
+  public function getInstallPathCallback(Package $package): string {
+    $name = explode('/', $package->getName())[1];
+
+    return vfsStream::url(
+      $this->rootDirectory->path() . '/' . static::LIBRARIES_DIRECTORY . '/' . $name
+    );
+  }
+
+  /**
+   * Callback for the LocalRepository getCanonicalPackages function.
+   */
+  public function getCanonicalPackagesCallback() {
+    $root_package = $this->composer->getPackage();
+    /**
+     * @var $dependencies Link[]
+     */
+    $dependencies = array_merge($root_package->getRequires(), $root_package->getDevRequires());
+    $return = [];
+
+    foreach ($dependencies as $dependency) {
+      /* @see setupVirtualFilesystem
+       * Create pseudo dependency packages, reading from the virtual filesystem.
+       */
+      $composer_path = 'vendor/' . $dependency->getTarget() . '/composer.json';
+      $this->assertTrue($this->rootDirectory->hasChild($composer_path));
+      $json = json_decode(
+        file_get_contents($this->rootDirectory->getChild($composer_path)->url()),
+        TRUE
+      );
+      $data = array_merge(
+        [
+          'name' => 'undefined',
+          'extra' => [],
+        ],
+        $json
+      );
+
+      $package = $this->createMock(Package::class);
+      $package->expects($this->atLeastOnce())->method('getExtra')->willReturn($data['extra']);
+      $package->method('getName')->willReturn($data['name']);
+      $return[] = $package;
+    }
+
+    return $return;
+  }
+
+  /**
+   * Create the libraries package structure.
+   *
+   * @param string $json_file
+   *   The library structure JSON file.
+   */
+  protected function createLibrariesPackageStructures(string $json_file) {
+    // Create the directory structure for the libraries so that they exist on
+    // disk for Finder to work with.
+    vfsStream::create(
+      [
+        static::LIBRARIES_DIRECTORY => json_decode(
+          file_get_contents($json_file),
+          TRUE
+        ),
+      ]
+    );
+  }
+
+}
diff --git a/tests/fixtures/all-dependency-libraries/composer.json b/tests/fixtures/all-dependency-libraries/composer.json
new file mode 100644
index 0000000..c7341bb
--- /dev/null
+++ b/tests/fixtures/all-dependency-libraries/composer.json
@@ -0,0 +1,8 @@
+{
+    "require": {
+        "zodiacmedia/drupal-libraries-test-dependency": "*@dev"
+    },
+    "extra": {
+        "drupal-libraries-dependencies": true
+    }
+}
diff --git a/tests/fixtures/all-dependency-libraries/installed-libraries.expected.json b/tests/fixtures/all-dependency-libraries/installed-libraries.expected.json
new file mode 100644
index 0000000..3191e2e
--- /dev/null
+++ b/tests/fixtures/all-dependency-libraries/installed-libraries.expected.json
@@ -0,0 +1,22 @@
+{
+  "schema-version": "1.0",
+  "installed": {
+    "test-library-dependency": {
+      "version": "1.0.0",
+      "url": "https://example.com/test-library-dependency.zip",
+      "type": "zip",
+      "ignore": [],
+      "package": "zodiacmedia/drupal-libraries-test-dependency"
+    },
+    "test-moment": {
+      "version": "2.25.0",
+      "url": "https://registry.npmjs.org/moment/-/moment-2.25.0.tgz",
+      "type": "tar",
+      "ignore": [
+        "*.md"
+      ],
+      "package": "zodiacmedia/drupal-libraries-test-dependency",
+      "shasum": "e961ab9a5848a1cf2c52b1af4e6c82a8401e7fe9"
+    }
+  }
+}
diff --git a/tests/fixtures/all-dependency-libraries/libraries-structure.json b/tests/fixtures/all-dependency-libraries/libraries-structure.json
new file mode 100644
index 0000000..4e9c0dd
--- /dev/null
+++ b/tests/fixtures/all-dependency-libraries/libraries-structure.json
@@ -0,0 +1,10 @@
+{
+  "test-library-dependency": {
+    "index.js": "",
+    "README.md": ""
+  },
+  "test-moment": {
+    "moment.js": "",
+    "README.md": ""
+  }
+}
diff --git a/tests/fixtures/download-and-ignore-library-files/composer.json b/tests/fixtures/download-and-ignore-library-files/composer.json
new file mode 100644
index 0000000..a97a421
--- /dev/null
+++ b/tests/fixtures/download-and-ignore-library-files/composer.json
@@ -0,0 +1,30 @@
+{
+    "extra": {
+        "drupal-libraries": {
+            "flexslider": {
+                "url": "https://github.com/woocommerce/FlexSlider/archive/2.6.4.zip",
+                "version": "2.6.4",
+                "type": "zip",
+                "ignore": [
+                    "bower_components",
+                    "demo",
+                    "node_modules"
+                ]
+            },
+            "moment": {
+                "url": "https://registry.npmjs.org/moment/-/moment-2.25.0.tgz",
+                "shasum": "e961ab9a5848a1cf2c52b1af4e6c82a8401e7fe9"
+            },
+            "select2": {
+                "url": "https://github.com/select2/select2/archive/4.0.13.zip",
+                "ignore": [
+                    ".*",
+                    "*.{md}",
+                    "Gruntfile.js",
+                    "{docs,src,tests}"
+                ]
+            },
+            "simple-color": "https://github.com/recurser/jquery-simple-color/archive/v1.2.2.zip"
+        }
+    }
+}
diff --git a/tests/fixtures/download-and-ignore-library-files/installed-libraries.expected.json b/tests/fixtures/download-and-ignore-library-files/installed-libraries.expected.json
new file mode 100644
index 0000000..582531d
--- /dev/null
+++ b/tests/fixtures/download-and-ignore-library-files/installed-libraries.expected.json
@@ -0,0 +1,43 @@
+{
+  "schema-version": "1.0",
+  "installed": {
+    "flexslider": {
+      "version": "2.6.4",
+      "url": "https://github.com/woocommerce/FlexSlider/archive/2.6.4.zip",
+      "type": "zip",
+      "ignore": [
+        "bower_components",
+        "demo",
+        "node_modules"
+      ],
+      "package": "drupal-libraries-installer-test/root-package"
+    },
+    "moment": {
+      "version": "2.25.0",
+      "url": "https://registry.npmjs.org/moment/-/moment-2.25.0.tgz",
+      "type": "tar",
+      "ignore": [],
+      "package": "drupal-libraries-installer-test/root-package",
+      "shasum": "e961ab9a5848a1cf2c52b1af4e6c82a8401e7fe9"
+    },
+    "select2": {
+      "version": "4.0.13",
+      "url": "https://github.com/select2/select2/archive/4.0.13.zip",
+      "type": "zip",
+      "ignore": [
+        ".*",
+        "*.{md}",
+        "Gruntfile.js",
+        "{docs,src,tests}"
+      ],
+      "package": "drupal-libraries-installer-test/root-package"
+    },
+    "simple-color": {
+      "version": "v1.2.2",
+      "url": "https://github.com/recurser/jquery-simple-color/archive/v1.2.2.zip",
+      "type": "zip",
+      "ignore": [],
+      "package": "drupal-libraries-installer-test/root-package"
+    }
+  }
+}
diff --git a/tests/fixtures/download-and-ignore-library-files/libraries-structure.json b/tests/fixtures/download-and-ignore-library-files/libraries-structure.json
new file mode 100644
index 0000000..54b058e
--- /dev/null
+++ b/tests/fixtures/download-and-ignore-library-files/libraries-structure.json
@@ -0,0 +1,55 @@
+{
+  "flexslider": {
+    "bower_components": {
+      ".text.txt": "",
+      "test.php": "",
+      "text.txt": ""
+    },
+    "demo": {
+      "index.html": "",
+      "demo.js": "",
+      "demo.css": "",
+      "Gruntfile.js": ""
+    },
+    "node_modules": {
+      "sub_module1": [],
+      "sub_module2": [],
+      "sub_module3": []
+    },
+    ".hidden.txt": "",
+    "Gruntfile.js": "",
+    "README.md": ""
+  },
+  "moment": {
+    "moment.js": ""
+  },
+  "select2": {
+    ".git": [],
+    ".hidden_directory": [],
+    "directory-with-hidden-file": {
+      ".should-not-be-removed.txt": ""
+    },
+    "docs": {
+      "index.html": "",
+      "readme.md": "",
+      "changes.rst": ""
+    },
+    "empty_directory": [],
+    "src": {
+      "index.js": "",
+      "style.css": "",
+      "index.html": ""
+    },
+    "tests": {
+      "Test.php": "",
+      "test.js": "",
+      "Gruntfile.js": ""
+    },
+    ".hidden.txt": "",
+    "Gruntfile.js": "",
+    "README.md": ""
+  },
+  "simple-color": {
+    "simple-color.js": ""
+  }
+}
diff --git a/tests/fixtures/existing-lock-file/composer.json b/tests/fixtures/existing-lock-file/composer.json
new file mode 100644
index 0000000..3d9cd46
--- /dev/null
+++ b/tests/fixtures/existing-lock-file/composer.json
@@ -0,0 +1,7 @@
+{
+    "extra": {
+        "drupal-libraries": {
+            "simple-color": "https://github.com/recurser/jquery-simple-color/archive/v1.2.2.zip"
+        }
+    }
+}
diff --git a/tests/fixtures/existing-lock-file/installed-libraries.expected.json b/tests/fixtures/existing-lock-file/installed-libraries.expected.json
new file mode 100644
index 0000000..0ac0bca
--- /dev/null
+++ b/tests/fixtures/existing-lock-file/installed-libraries.expected.json
@@ -0,0 +1,12 @@
+{
+  "schema-version": "1.0",
+  "installed": {
+    "simple-color": {
+      "version": "v1.2.2",
+      "url": "https://github.com/recurser/jquery-simple-color/archive/v1.2.2.zip",
+      "type": "zip",
+      "ignore": [],
+      "package": "drupal-libraries-installer-test/root-package"
+    }
+  }
+}
diff --git a/tests/fixtures/existing-lock-file/installed-libraries.initial.json b/tests/fixtures/existing-lock-file/installed-libraries.initial.json
new file mode 100644
index 0000000..0ac0bca
--- /dev/null
+++ b/tests/fixtures/existing-lock-file/installed-libraries.initial.json
@@ -0,0 +1,12 @@
+{
+  "schema-version": "1.0",
+  "installed": {
+    "simple-color": {
+      "version": "v1.2.2",
+      "url": "https://github.com/recurser/jquery-simple-color/archive/v1.2.2.zip",
+      "type": "zip",
+      "ignore": [],
+      "package": "drupal-libraries-installer-test/root-package"
+    }
+  }
+}
diff --git a/tests/fixtures/existing-lock-file/libraries-structure.json b/tests/fixtures/existing-lock-file/libraries-structure.json
new file mode 100644
index 0000000..b58e30f
--- /dev/null
+++ b/tests/fixtures/existing-lock-file/libraries-structure.json
@@ -0,0 +1,5 @@
+{
+  "simple-color": {
+    "simple-color.js": ""
+  }
+}
diff --git a/tests/fixtures/specific-dependency-libraries-with-override/composer.json b/tests/fixtures/specific-dependency-libraries-with-override/composer.json
new file mode 100644
index 0000000..fd09852
--- /dev/null
+++ b/tests/fixtures/specific-dependency-libraries-with-override/composer.json
@@ -0,0 +1,16 @@
+{
+    "require": {
+        "zodiacmedia/drupal-libraries-test-dependency": "*@dev"
+    },
+    "extra": {
+        "drupal-libraries-dependencies": [
+            "zodiacmedia/drupal-libraries-test-dependency"
+        ],
+        "drupal-libraries": {
+            "test-moment": {
+                "url": "https://assets.example.com/moment-override.zip",
+                "ignore": []
+            }
+        }
+    }
+}
diff --git a/tests/fixtures/specific-dependency-libraries-with-override/installed-libraries.expected.json b/tests/fixtures/specific-dependency-libraries-with-override/installed-libraries.expected.json
new file mode 100644
index 0000000..55f02f1
--- /dev/null
+++ b/tests/fixtures/specific-dependency-libraries-with-override/installed-libraries.expected.json
@@ -0,0 +1,19 @@
+{
+  "schema-version": "1.0",
+  "installed": {
+    "test-moment": {
+      "version": "1.0.0",
+      "url": "https://assets.example.com/moment-override.zip",
+      "type": "zip",
+      "ignore": [],
+      "package": "drupal-libraries-installer-test/root-package"
+    },
+    "test-library-dependency": {
+      "version": "1.0.0",
+      "url": "https://example.com/test-library-dependency.zip",
+      "type": "zip",
+      "ignore": [],
+      "package": "zodiacmedia/drupal-libraries-test-dependency"
+    }
+  }
+}
diff --git a/tests/fixtures/specific-dependency-libraries-with-override/libraries-structure.json b/tests/fixtures/specific-dependency-libraries-with-override/libraries-structure.json
new file mode 100644
index 0000000..4e9c0dd
--- /dev/null
+++ b/tests/fixtures/specific-dependency-libraries-with-override/libraries-structure.json
@@ -0,0 +1,10 @@
+{
+  "test-library-dependency": {
+    "index.js": "",
+    "README.md": ""
+  },
+  "test-moment": {
+    "moment.js": "",
+    "README.md": ""
+  }
+}
diff --git a/tests/fixtures/specific-dependency-libraries/composer.json b/tests/fixtures/specific-dependency-libraries/composer.json
new file mode 100644
index 0000000..3142496
--- /dev/null
+++ b/tests/fixtures/specific-dependency-libraries/composer.json
@@ -0,0 +1,10 @@
+{
+    "require": {
+        "zodiacmedia/drupal-libraries-test-dependency": "*@dev"
+    },
+    "extra": {
+        "drupal-libraries-dependencies": [
+            "zodiacmedia/drupal-libraries-test-dependency"
+        ]
+    }
+}
diff --git a/tests/fixtures/specific-dependency-libraries/installed-libraries.expected.json b/tests/fixtures/specific-dependency-libraries/installed-libraries.expected.json
new file mode 100644
index 0000000..3191e2e
--- /dev/null
+++ b/tests/fixtures/specific-dependency-libraries/installed-libraries.expected.json
@@ -0,0 +1,22 @@
+{
+  "schema-version": "1.0",
+  "installed": {
+    "test-library-dependency": {
+      "version": "1.0.0",
+      "url": "https://example.com/test-library-dependency.zip",
+      "type": "zip",
+      "ignore": [],
+      "package": "zodiacmedia/drupal-libraries-test-dependency"
+    },
+    "test-moment": {
+      "version": "2.25.0",
+      "url": "https://registry.npmjs.org/moment/-/moment-2.25.0.tgz",
+      "type": "tar",
+      "ignore": [
+        "*.md"
+      ],
+      "package": "zodiacmedia/drupal-libraries-test-dependency",
+      "shasum": "e961ab9a5848a1cf2c52b1af4e6c82a8401e7fe9"
+    }
+  }
+}
diff --git a/tests/fixtures/specific-dependency-libraries/libraries-structure.json b/tests/fixtures/specific-dependency-libraries/libraries-structure.json
new file mode 100644
index 0000000..4e9c0dd
--- /dev/null
+++ b/tests/fixtures/specific-dependency-libraries/libraries-structure.json
@@ -0,0 +1,10 @@
+{
+  "test-library-dependency": {
+    "index.js": "",
+    "README.md": ""
+  },
+  "test-moment": {
+    "moment.js": "",
+    "README.md": ""
+  }
+}