diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationCollector.php b/core/lib/Drupal/Core/Authentication/AuthenticationCollector.php
index e417f50..60bd62c 100644
--- a/core/lib/Drupal/Core/Authentication/AuthenticationCollector.php
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationCollector.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * @file
  * Contains \Drupal\Core\Authentication\AuthenticationCollector.
@@ -6,8 +7,6 @@
 
 namespace Drupal\Core\Authentication;
 
-use Drupal\Core\Authentication\AuthenticationProviderInterface;
-
 /**
  * A collector class for authentication providers.
  */
@@ -47,7 +46,7 @@ class AuthenticationCollector implements AuthenticationCollectorInterface {
   public function addProvider(AuthenticationProviderInterface $provider, $provider_id, $priority = 0, $global = FALSE) {
     $this->providers[$provider_id] = $provider;
     $this->providerOrders[$priority][$provider_id] = $provider;
-    // Force the builders to be re-sorted.
+    // Force the providers to be re-sorted.
     $this->sortedProviders = NULL;
 
     if ($global) {
@@ -74,7 +73,7 @@ public function getProvider($provider_id) {
    */
   public function getSortedProviders() {
     if (!isset($this->sortedProviders)) {
-      // Sort the builders according to priority.
+      // Sort the providers according to priority.
       krsort($this->providerOrders);
 
       // Merge nested providers from $this->providers into $this->sortedProviders.
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php b/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php
index 76b7fd2..5bf6a08 100644
--- a/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php
@@ -8,7 +8,7 @@
 namespace Drupal\Core\Authentication;
 
 /**
- * A collector class for authentication providers.
+ * Interface for collectors of registered authentication providers.
  */
 interface AuthenticationCollectorInterface {
 
@@ -30,6 +30,9 @@ public function addProvider(AuthenticationProviderInterface $provider, $provider
   /**
    * Returns whether a provider is considered global.
    *
+   * @param string $provider_id
+   *   The provider ID.
+   *
    * @return bool
    *   TRUE if the provider is global, FALSE otherwise.
    *
@@ -41,7 +44,7 @@ public function isGlobal($provider_id);
    * Returns an authentication provider.
    *
    * @param string $provider_id
-   *   THe provider ID.
+   *   The provider ID.
    *
    * @return \Drupal\Core\Authentication\AuthenticationProviderInterface|NULL
    *   The authentication provider which matches the ID.
@@ -51,9 +54,6 @@ public function getProvider($provider_id);
   /**
    * Returns the sorted array of authentication providers.
    *
-   * @todo Replace with a list of providers sorted during compile time in
-   *   https://www.drupal.org/node/2432585.
-   *
    * @return \Drupal\Core\Authentication\AuthenticationProviderInterface[]
    *   An array of authentication provider objects.
    */
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationManager.php b/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
index 455e5a6..9f4c841 100644
--- a/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
@@ -20,28 +20,7 @@
  *
  * If no provider set an active user then the user is set to anonymous.
  */
-class AuthenticationManager implements AuthenticationProviderInterface, AuthenticationProviderFilterInterface, AuthenticationProviderChallengeInterface, AuthenticationManagerInterface {
-
-  /**
-   * Array of all registered authentication providers, keyed by ID.
-   *
-   * @var \Drupal\Core\Authentication\AuthenticationProviderInterface[]
-   */
-  protected $providers;
-
-  /**
-   * Array of all providers and their priority.
-   *
-   * @var array
-   */
-  protected $providerOrders = array();
-
-  /**
-   * Sorted list of registered providers.
-   *
-   * @var \Drupal\Core\Authentication\AuthenticationProviderInterface[]
-   */
-  protected $sortedProviders;
+class AuthenticationManager implements AuthenticationProviderInterface, AuthenticationProviderFilterInterface, AuthenticationProviderChallengeInterface {
 
   /**
    * List of providers which implement the filter interface.
@@ -58,10 +37,15 @@ class AuthenticationManager implements AuthenticationProviderInterface, Authenti
   protected $challengers;
 
   /**
+   * The authentication provider collector.
+   *
    * @var \Drupal\Core\Authentication\AuthenticationCollectorInterface
    */
   protected $authCollector;
 
+  /**
+   * Creates a new authentication manager instance.
+   */
   public function __construct(AuthenticationCollectorInterface $auth_collector) {
     $this->authCollector = $auth_collector;
 
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationManagerInterface.php b/core/lib/Drupal/Core/Authentication/AuthenticationManagerInterface.php
deleted file mode 100644
index d17f2ff..0000000
--- a/core/lib/Drupal/Core/Authentication/AuthenticationManagerInterface.php
+++ /dev/null
@@ -1,15 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Authentication\AuthenticationManagerInterface.
- */
-
-namespace Drupal\Core\Authentication;
-
-/**
- * Defines an interface for authentication managers.
- */
-interface AuthenticationManagerInterface {
-
-}
diff --git a/core/tests/Drupal/Tests/Core/Authentication/AuthenticationCollectorTest.php b/core/tests/Drupal/Tests/Core/Authentication/AuthenticationCollectorTest.php
new file mode 100644
index 0000000..e4d88fc
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Authentication/AuthenticationCollectorTest.php
@@ -0,0 +1,83 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Core\Authentication\AuthenticationCollectorTest.
+ */
+
+namespace Drupal\Tests\Core\Authentication;
+
+use Drupal\Core\Authentication\AuthenticationCollector;
+use Drupal\Core\Authentication\AuthenticationProviderInterface;
+use Drupal\Tests\UnitTestCase;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * @coversDefaultClass \Drupal\Core\Authentication\AuthenticationCollector
+ * @group Authentication
+ */
+class AuthenticationCollectorTest extends UnitTestCase {
+
+  /**
+   * @covers ::addProvider
+   * @covers ::getSortedProviders
+   * @covers ::getProvider
+   * @covers ::isGlobal
+   */
+  public function testAuthenticationCollector() {
+    $providers = [];
+    $global = [];
+    $authentication_collector = new AuthenticationCollector();
+    for ($i=0; $i<10; $i++) {
+      $provider_id = $this->randomMachineName();
+      $priority = rand(-100,100);
+      $provider = new TestAuthenticationProvider($provider_id);
+      $providers[$priority] = $provider;
+      $global[$provider_id] = rand(0,1) > 0.5;
+      $authentication_collector->addProvider($provider, $provider_id, $priority, $global[$provider_id]);
+    }
+    // Sort the $providers array by priority (highest number is lowest priority)
+    // and compare with AuthenticationCollector::getSortedProviders().
+    krsort($providers);
+    $this->assertEquals(array_values($providers), array_values($authentication_collector->getSortedProviders()));
+
+    // Test AuthenticationCollector::getProvider() and AuthenticationCollector::isGlobal().
+    foreach ($providers as $provider) {
+      $this->assertEquals($provider, $authentication_collector->getProvider($provider->providerId));
+      $this->assertEquals($global[$provider->providerId], $authentication_collector->isGlobal($provider->providerId));
+    }
+  }
+
+}
+
+class TestAuthenticationProvider implements AuthenticationProviderInterface {
+
+  /**
+   * The provider id.
+   *
+   * @var $provider_id
+   */
+  public $providerId;
+
+  /**
+   * Constructor.
+   */
+  public function __construct($provider_id) {
+    $this->providerId = $provider_id;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies(Request $request) {
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function authenticate(Request $request) {
+    return NULL;
+  }
+
+}