diff --git a/ng_lightbox.info.yml b/ng_lightbox.info.yml
index e601c6e..1696a87 100644
--- a/ng_lightbox.info.yml
+++ b/ng_lightbox.info.yml
@@ -2,6 +2,7 @@ name: NG Lightbox
 description: A path based lightbox solution using CSS 3 properties.
 type: module
 core: 8.x
+core_version_requirement: '^8 || ^9'
 package: NG
 configure: ng_lightbox.settings
 
diff --git a/ng_lightbox.services.yml b/ng_lightbox.services.yml
index 96b1564..4212e6f 100644
--- a/ng_lightbox.services.yml
+++ b/ng_lightbox.services.yml
@@ -1,4 +1,4 @@
 services:
   ng_lightbox:
     class: Drupal\ng_lightbox\NgLightbox
-    arguments: ['@path.matcher', '@path.alias_manager', '@config.factory', '@router.admin_context']
+    arguments: ['@path.matcher', '@path_alias.manager', '@config.factory', '@router.admin_context']
diff --git a/src/NgLightbox.php b/src/NgLightbox.php
index 874a0ff..f0342fd 100644
--- a/src/NgLightbox.php
+++ b/src/NgLightbox.php
@@ -3,13 +3,14 @@
 namespace Drupal\ng_lightbox;
 
 use Drupal\Core\Config\ConfigFactoryInterface;
-use Drupal\Core\Path\AliasManagerInterface;
+use Drupal\path_alias\AliasManagerInterface;
 use Drupal\Core\Path\PathMatcherInterface;
 use Drupal\Core\Routing\AdminContext;
-use Drupal\Core\Routing\RouteMatch;
 use Drupal\Core\Url;
-use Symfony\Component\HttpFoundation\Request;
 
+/**
+ * Provides a Service Class for NgLightbox.
+ */
 class NgLightbox {
 
   /**
@@ -18,21 +19,29 @@ class NgLightbox {
   const DEFAULT_MODAL = 'drupal_modal';
 
   /**
+   * Provides an interface for URL path matchers.
+   *
    * @var \Drupal\Core\Path\PathMatcherInterface
    */
   protected $pathMatcher;
 
   /**
-   * @var \Drupal\Core\Path\AliasManagerInterface
+   * Find an alias for a path and vice versa.
+   *
+   * @var \Drupal\path_alias\AliasManagerInterface
    */
   protected $aliasManager;
 
   /**
+   * Defines the immutable configuration object.
+   *
    * @var \Drupal\Core\Config\ImmutableConfig
    */
   protected $config;
 
   /**
+   * Provides a helper class to determine whether the route is an admin one.
+   *
    * @var \Drupal\Core\Routing\AdminContext
    */
   protected $adminContext;
@@ -49,10 +58,14 @@ class NgLightbox {
    *
    * @param \Drupal\Core\Path\PathMatcherInterface $path_matcher
    *   Patch matcher services for comparing the lightbox patterns.
-   * @param \Drupal\Core\Path\AliasManagerInterface $alias_manager
+   * @param \Drupal\path_alias\AliasManagerInterface $alias_manager
    *   Alias manager so we can also test path aliases.
+   *   The Path Alias core subsystem has been moved to the "path_alias" module
+   *   [https://www.drupal.org/node/3092086].
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
    *   The config factory so we can get the lightbox settings.
+   * @param \Drupal\Core\Routing\AdminContext $admin_context
+   *   Provides a helper class to determine whether the route is an admin one.
    */
   public function __construct(PathMatcherInterface $path_matcher, AliasManagerInterface $alias_manager, ConfigFactoryInterface $config_factory, AdminContext $admin_context) {
     $this->pathMatcher = $path_matcher;
@@ -107,7 +120,7 @@ class NgLightbox {
     // Normalise the patterns as well so they match the normalised paths.
     $patterns = strtolower($this->config->get('patterns'));
 
-    // Check for internal paths first which is much quicker than the alias lookup.
+    // Check for internal paths first which is much quicker than alias lookup.
     if ($this->pathMatcher->matchPath($path, $patterns)) {
       $this->matches[$path] = TRUE;
     }
diff --git a/src/NgLightboxPass.php b/src/NgLightboxPass.php
index 7dca32e..ef1e69e 100644
--- a/src/NgLightboxPass.php
+++ b/src/NgLightboxPass.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\ng_lightbox\NgLightboxPass
- */
-
 namespace Drupal\ng_lightbox;
 
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
diff --git a/src/NgLightboxServiceProvider.php b/src/NgLightboxServiceProvider.php
index cb12d58..4757d4e 100644
--- a/src/NgLightboxServiceProvider.php
+++ b/src/NgLightboxServiceProvider.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\ng_lightbox\NgLightboxServiceProvider
- */
-
 namespace Drupal\ng_lightbox;
 
 use Drupal\Core\DependencyInjection\ContainerBuilder;
@@ -31,9 +26,14 @@ class NgLightboxServiceProvider extends ServiceProviderBase {
   }
 
   /**
+   * Function for addLightBox.
+   *
    * @param \Drupal\Core\DependencyInjection\ContainerBuilder $container
-   * @param $id
-   * @param $title
+   *   Drupal's dependency injection container builder.
+   * @param string $id
+   *   The ID of the main content render box.
+   * @param string $title
+   *   The title of the box.
    */
   protected function addLightbox(ContainerBuilder $container, $id, $title) {
     $definition = $container->getDefinition($id);
diff --git a/src/Tests/NgLightboxTest.php b/src/Tests/NgLightboxTest.php
index b0a9e44..20c54f4 100644
--- a/src/Tests/NgLightboxTest.php
+++ b/src/Tests/NgLightboxTest.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * NG Lightbox tests.
- */
-
 namespace Drupal\ng_lightbox\Tests;
 
 use Drupal\Core\Link;
@@ -20,6 +15,8 @@ use Drupal\KernelTests\KernelTestBase;
 class NgLightboxTest extends KernelTestBase {
 
   /**
+   * Modules to install.
+   *
    * @var array
    */
   public static $modules = ['system', 'node', 'user', 'ng_lightbox'];
@@ -29,12 +26,12 @@ class NgLightboxTest extends KernelTestBase {
    */
   public function setUp() {
     parent::setUp();
-    $this->installSchema('system', ['router', 'url_alias']);
+    // $this->installSchema('system', ['router', 'url_alias']);
     \Drupal::service('router.builder')->rebuild();
 
     $this->installEntitySchema('node');
     $this->installEntitySchema('user');
-    $this->installSchema('node', ['node_access']);
+    // $this->installSchema('node', ['node_access']);
     $this->installConfig(['ng_lightbox']);
 
     // Create the node type.
@@ -49,15 +46,16 @@ class NgLightboxTest extends KernelTestBase {
     // Test the patterns are enabled on links as expected.
     $node = Node::create(['type' => 'page', 'title' => $this->randomString()]);
     $node->save();
-    $config = \Drupal::configFactory()->getEditable('ng_lightbox.settings');
-    $config->set('patterns', $node->toUrl())->save();
+    $value_patterns = $node->toUrl()->toString();
+    $config = \Drupal::configFactory()->getEditable('ng_lightbox.settings')
+              ->set('patterns', $value_patterns)
+              ->save();
     $this->assertLightboxEnabled(Link::fromTextAndUrl('Normal Path', $node->toUrl()));
 
     // Create a second node and make sure it doesn't get lightboxed.
-    $node = Node::create(['type' => 'page', 'title' => $this->randomString()]);
-    $node->save();
-    $this->assertLightboxNotEnabled(Link::fromTextAndUrl('Normal Path', $node->toUrl()));
-
+    $secondnode = Node::create(['type' => 'page', 'title' => $this->randomString()]);
+    $secondnode->save();
+    $this->assertLightboxNotEnabled(Link::fromTextAndUrl('Second Path', $secondnode->toUrl()));
 
     // @TODO, these were in D7 but in D8, I can't see how you can even generate
     // a link with such a format so maybe it isn't needed at all?
@@ -74,8 +72,8 @@ class NgLightboxTest extends KernelTestBase {
    *   The rendered link.
    */
   protected function assertLightboxEnabled($link) {
-    $this->assertContains('use-ajax', $link);
-    $this->assertContains('data-dialog-type', $link);
+    $this->assertStringContainsString('use-ajax', $link->toString());
+    $this->assertStringContainsString('data-dialog-type', $link->toString());
   }
 
   /**
@@ -85,48 +83,8 @@ class NgLightboxTest extends KernelTestBase {
    *   The rendered link.
    */
   protected function assertLightboxNotEnabled($link) {
-    $this->assertNotContains('use-ajax', $link);
-    $this->assertNotContains('data-dialog-type', $link);
-  }
-
-  /**
-   * Asserts a string does exist in the haystack.
-   *
-   * @param string $needle
-   *   The string to search for.
-   * @param string $haystack
-   *   The string to search within.
-   * @param string $message
-   *   The message to log.
-   *
-   * @return bool
-   *   TRUE if it was found otherwise FALSE.
-   */
-  protected function assertContains($needle, $haystack, $message = '') {
-    if (empty($message)) {
-      $message = t('%needle was found within %haystack', ['%needle' => $needle, '%haystack' => $haystack]);
-    }
-    return $this->assertTrue(stripos($haystack, $needle) !== FALSE, $message);
-  }
-
-  /**
-   * Asserts a string does not exist in the haystack.
-   *
-   * @param string $needle
-   *   The string to search for.
-   * @param string $haystack
-   *   The string to search within.
-   * @param string $message
-   *   The message to log.
-   *
-   * @return bool
-   *   TRUE if it was not found otherwise FALSE.
-   */
-  protected function assertNotContains($needle, $haystack, $message = '') {
-    if (empty($message)) {
-      $message = t('%needle was not found within %haystack', ['%needle' => $needle, '%haystack' => $haystack]);
-    }
-    return $this->assertTrue(stripos($haystack, $needle) === FALSE, $message);
+    $this->assertNotContains('use-ajax', $link->toRenderable());
+    $this->assertNotContains('data-dialog-type', $link->toRenderable());
   }
 
 }
diff --git a/src/Tests/NgLightboxWebTest.php b/src/Tests/NgLightboxWebTest.php
index ec989bc..20e4f5b 100644
--- a/src/Tests/NgLightboxWebTest.php
+++ b/src/Tests/NgLightboxWebTest.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\ng_lightbox\Tests\NgLightboxWebTest
- */
-
 namespace Drupal\ng_lightbox\Tests;
 
 use Drupal\simpletest\WebTestBase;
@@ -16,10 +11,13 @@ use Drupal\simpletest\WebTestBase;
  */
 class NgLightboxWebTest extends WebTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
   protected $profile = 'minimal';
 
   /**
-   * Default modules to enable.
+   * Modules to install.
    *
    * @var array
    */
diff --git a/tests/src/Kernel/NgLightboxTest.php b/tests/src/Kernel/NgLightboxTest.php
index f01a890..6205caf 100644
--- a/tests/src/Kernel/NgLightboxTest.php
+++ b/tests/src/Kernel/NgLightboxTest.php
@@ -13,9 +13,11 @@ use Drupal\KernelTests\KernelTestBase;
 class NgLightboxTest extends KernelTestBase {
 
   /**
-   * {@inheritdoc}
+   * Modules to install.
+   *
+   * @var array
    */
-  static $modules = ['system', 'ng_lightbox'];
+  public static $modules = ['system', 'ng_lightbox'];
 
   /**
    * Test a URL that only has a hash.
diff --git a/tests/src/Unit/NgLightboxTest.php b/tests/src/Unit/NgLightboxTest.php
index eaa5d8b..a86d1ec 100644
--- a/tests/src/Unit/NgLightboxTest.php
+++ b/tests/src/Unit/NgLightboxTest.php
@@ -1,10 +1,5 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\Tests\ng_lightbox\Unit\NgLightboxTest
- */
-
 namespace Drupal\Tests\ng_lightbox\Unit;
 
 use Drupal\ng_lightbox\NgLightbox;
@@ -47,7 +42,7 @@ class NgLightboxTest extends UnitTestCase {
   /**
    * Helper to create Url mocks.
    *
-   * @param bool|FALSE $is_external
+   * @param bool|false $is_external
    *   TRUE if this URL is external otherwise FALSE.
    *
    * @return \Prophecy\Prophecy\ObjectProphecy
@@ -68,7 +63,8 @@ class NgLightboxTest extends UnitTestCase {
   protected function getLightbox($skip_admin_paths = TRUE, $is_admin_route = TRUE) {
 
     $path_matcher = $this->prophesize('Drupal\Core\Path\PathMatcherInterface');
-    $alias_manager = $this->prophesize('Drupal\Core\Path\AliasManagerInterface');
+    // The Path Alias core subsystem has been moved to the "path_alias" module.
+    $alias_manager = $this->prophesize('Drupal\path_alias\AliasManagerInterface');
     $config_factory = $this->prophesize('Drupal\Core\Config\ConfigFactoryInterface');
     $config = $this->prophesize('Drupal\Core\Config\ImmutableConfig');
     $config->get(Argument::exact('skip_admin_paths'))->willReturn($skip_admin_paths);