diff --git a/core/core.services.yml b/core/core.services.yml
index 969b0e0..1de4ce9 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -4,6 +4,9 @@ services:
     arguments: ['@settings']
     calls:
       - [setContainer, ['@service_container']]
+  cache_contexts:
+    class: Drupal\Core\Cache\CacheContexts
+    arguments: ['@service_container', '%cache_contexts%' ]
   cache.backend.database:
     class: Drupal\Core\Cache\DatabaseBackendFactory
     arguments: ['@database']
@@ -640,6 +643,11 @@ services:
   date:
     class: Drupal\Core\Datetime\Date
     arguments: ['@entity.manager', '@language_manager', '@string_translation', '@config.factory']
+  http.request_cache_contexts:
+    class: Drupal\Core\Http\RequestCacheContexts
+    arguments: ['@request']
+    tags:
+      - { name: cache.context}
   feed.bridge.reader:
     class: Drupal\Component\Bridge\ZfExtensionManagerSfContainer
     calls:
diff --git a/core/includes/common.inc b/core/includes/common.inc
index 0f47bb2..524e304 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -10,7 +10,6 @@
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Component\Utility\Xss;
 use Drupal\Core\Cache\Cache;
-use Drupal\Core\Cache\CacheableHelper;
 use Drupal\Core\Language\Language;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpFoundation\Request;
@@ -4536,8 +4535,7 @@ function drupal_cache_tags_page_get(Response $response) {
  */
 function drupal_render_cache_by_query($query, $function, $expire = Cache::PERMANENT, $granularity = NULL) {
   $cache_keys = array_merge(array($function), drupal_render_cid_parts($granularity));
-  $query->preExecute();
-  $cache_keys[] = hash('sha256', serialize(array((string) $query, $query->getArguments())));
+  $cache_keys[] = Cache::keyFromQuery($query);
   return array(
     '#query' => $query,
     '#pre_render' => array($function . '_pre_render'),
@@ -4615,8 +4613,8 @@ function drupal_render_cid_create($elements) {
   }
   elseif (isset($elements['#cache']['keys'])) {
     // Add cache context keys when constants are used in the 'keys' parameter.
-    $cacheable_helper = new CacheableHelper;
-    $keys = $cacheable_helper->addCacheContextsToKeys($elements['#cache']['keys']);
+    $cacheable_helper = \Drupal::service("cache_contexts");
+    $keys = $cacheable_helper->addContextsToKeys($elements['#cache']['keys']);
 
     $granularity = isset($elements['#cache']['granularity']) ? $elements['#cache']['granularity'] : NULL;
     // Merge in additional cache ID parts based provided by drupal_render_cid_parts().
diff --git a/core/lib/Drupal/Core/Cache/Cache.php b/core/lib/Drupal/Core/Cache/Cache.php
index c2f5fe6..25e15bb 100644
--- a/core/lib/Drupal/Core/Cache/Cache.php
+++ b/core/lib/Drupal/Core/Cache/Cache.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\Core\Cache;
 
+use Drupal\Core\Database\Query\SelectInterface;
+
 /**
  * Helper methods for cache.
  */
@@ -70,4 +72,19 @@ public static function getBins() {
     return $bins;
   }
 
+  /**
+   * Generates a hash from a query object, to be used as part of the cache key
+   *
+   * @param $query
+   *   A select query object.
+   *
+   * @return string
+   *   A hash of the query arguments.
+   */
+  public static function keyFromQuery(SelectInterface $query) {
+    $query->preExecute();
+    $keys = array((string) $query, $query->getArguments());
+    return hash('sha256', serialize($keys));
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Cache/CacheContexts.php b/core/lib/Drupal/Core/Cache/CacheContexts.php
new file mode 100644
index 0000000..433bed9
--- /dev/null
+++ b/core/lib/Drupal/Core/Cache/CacheContexts.php
@@ -0,0 +1,123 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Cache\CacheContexts.
+ */
+
+namespace Drupal\Core\Cache;
+
+use Drupal\Core\Database\Query\SelectInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Contains all available cache contexts to convert string placeholders into
+ * their final string values, to be used as a cache key.
+ */
+class CacheContexts {
+
+
+  /**
+   * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
+   *   The current service container.
+   * @param array $contexts
+   *   An array of arrays that map cache context strings to services and the
+   *   callback methods that resolve the string into a cache key:
+   *
+   *     array(
+   *       "provider.some_context_name" => array(
+   *         "service" => "provider_service_id",
+   *         "callback" => "getSomeContext",
+   *       )
+   *     )
+   *
+   */
+  public function __construct(ContainerInterface $container, array $contexts) {
+    $this->container = $container;
+    $this->contexts = $contexts;
+  }
+
+  /**
+   * Provides an array of available cache contexts.
+   *
+   * @return array
+   *   An array of available cache contexts.
+   */
+  public function getAll() {
+    return array_keys($this->contexts);
+  }
+
+  /**
+   * Provides an array of available cache context labels, to be used used in a
+   * cache configuration form.
+   *
+   * @return array
+   *   An array of available cache context labels.
+   */
+  public function getLabels() {
+    $with_labels = array();
+    foreach ($this->contexts as $name => $params) {
+      $with_labels[$name] = $params["label"];
+    }
+    return $with_labels;
+  }
+
+  /**
+   * Converts cache contexts to string representations of the context.
+   *
+   * @param $keys
+   *   An array of cache keys that may or may not contain cache contexts.
+   * @return array
+   *   A copy of the input, with cache contexts converted.
+   */
+  public function addContextsToKeys($keys) {
+    $context_keys = array_intersect($keys, $this->getAll());
+    $new_keys = $keys;
+
+    // Iterate over the indices instead of the values so that the order of the
+    // cache keys are preserved.
+    foreach (array_keys($context_keys) as $index) {
+      $new_keys[$index] = $this->getContext($keys[$index]);
+    }
+    return $new_keys;
+  }
+
+  /**
+   * Provides the string representaton of a cache context.
+   *
+   * @todo Document this properly once the input arguments are decided on,
+   *   assuming the reuse of existing cache constants is temporary.
+   *
+   * @return string
+   *   The string representaton of a cache context.
+   */
+  protected function getContext($context) {
+    $context_info = $this->contexts[$context];
+    return call_user_func($this->getCallable($context_info));
+  }
+
+  /**
+   * @param array $context
+   * @return callable
+   *   A callable that returns the resolved cache context.
+   */
+  protected function getCallable($context) {
+    return array(
+      $this->getService($context["service"]),
+      $context["callback"]
+    );
+  }
+
+  /**
+   * Retrieves a service from the container.
+   *
+   * @param string $service
+   *   The ID of the service to retrieve.
+   * @return mixed
+   *   The specified service.
+   */
+  protected function getService($service) {
+    return $this->container->get($service);
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Cache/CacheContextsPass.php b/core/lib/Drupal/Core/Cache/CacheContextsPass.php
new file mode 100644
index 0000000..d5f87f0
--- /dev/null
+++ b/core/lib/Drupal/Core/Cache/CacheContextsPass.php
@@ -0,0 +1,34 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Cache\CacheContextsPass.
+ */
+
+namespace Drupal\Core\Cache;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+
+/**
+ * Adds cache_contexts parameter to the container.
+ */
+class CacheContextsPass implements CompilerPassInterface {
+
+  /**
+   * Implements CompilerPassInterface::process().
+   *
+   * Collects the cache contexts into the cache_contexts parameter.
+   */
+  public function process(ContainerBuilder $container) {
+    $cache_contexts = array();
+    foreach ($container->findTaggedServiceIds('cache.context') as $service_name => $attrs) {
+      $service = $container->getDefinition($service_name);
+      $class = $service->getClass();
+      foreach ($class::getCacheContexts() as $context => $params) {
+        $cache_contexts[$context] = $params + array("service" => $service_name);
+      }
+    }
+    $container->setParameter('cache_contexts', $cache_contexts);
+  }
+}
diff --git a/core/lib/Drupal/Core/Cache/CacheableHelper.php b/core/lib/Drupal/Core/Cache/CacheableHelper.php
deleted file mode 100644
index 88cc9af..0000000
--- a/core/lib/Drupal/Core/Cache/CacheableHelper.php
+++ /dev/null
@@ -1,91 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Cache\CacheableHelper.
- */
-
-namespace Drupal\Core\Cache;
-
-use Drupal\Core\Database\Query\SelectInterface;
-
-/**
- * A helper class that contains methods that could be useful to any object using
- * the Drupal Cache API.
- *
- * @todo Consider converting to a trait once traits are available.
- */
-class CacheableHelper {
-
-  /**
-   * Generates a hash from a query object, to be used as part of the cache key
-   *
-   * @param $query
-   *   A select query object.
-   *
-   * @return string
-   *   A hash of the query arguments.
-   */
-  function keyFromQuery(SelectInterface $query) {
-    $query->preExecute();
-    $keys = array((string) $query, $query->getArguments());
-    return hash('sha256', serialize($keys));
-  }
-
-  /**
-   * Converts cache contexts to string representations of the context.
-   *
-   * @param $keys
-   *   An array of cache keys that may or may not contain cache contexts.
-   * @return array
-   *   A copy of the input, with cache contexts converted.
-   */
-  function addCacheContextsToKeys($keys) {
-    $keys_with_contexts = array();
-    foreach ($keys as $key) {
-      $keys_with_contexts[] = $this->getContext($key) ?: $key;
-    }
-    return $keys_with_contexts;
-  }
-
-  /**
-   * Provides the string representaton of a cache context.
-   *
-   * @todo Document this properly once the input arguments are decided on,
-   *   assuming the reuse of existing cache constants is temporary.
-   *
-   * @return string
-   *   The string representaton of a cache context.
-   */
-  protected function getContext($context) {
-    switch ($context) {
-    case DRUPAL_CACHE_PER_PAGE:
-      // @todo: Make this use the request properly.
-      return $this->currentPath();
-    case DRUPAL_CACHE_PER_USER:
-      return "u." . $this->currentUser()->id();
-    case DRUPAL_CACHE_PER_ROLE:
-      return 'r.' . implode(',', $this->currentUser()->getRoles());
-    default:
-      return FALSE;
-    }
-  }
-
-  /**
-   * @return \Drupal\Core\Session\AccountInterface
-   *   The current user.
-   */
-  protected function currentUser() {
-    return \Drupal::currentUser();
-  }
-
-  /**
-   * @return string
-   *   The current path.
-   */
-  protected function currentPath() {
-    global $base_root;
-    return $base_root . request_uri();
-  }
-
-}
diff --git a/core/lib/Drupal/Core/CoreServiceProvider.php b/core/lib/Drupal/Core/CoreServiceProvider.php
index 847960c..1de7b19 100644
--- a/core/lib/Drupal/Core/CoreServiceProvider.php
+++ b/core/lib/Drupal/Core/CoreServiceProvider.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core;
 
 use Drupal\Core\Cache\ListCacheBinsPass;
+use Drupal\Core\Cache\CacheContextsPass;
 use Drupal\Core\DependencyInjection\ServiceProviderInterface;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\DependencyInjection\Compiler\ModifyServiceDefinitionsPass;
@@ -70,6 +71,7 @@ public function register(ContainerBuilder $container) {
     $container->addCompilerPass(new RegisterPathProcessorsPass());
     $container->addCompilerPass(new RegisterRouteProcessorsPass());
     $container->addCompilerPass(new ListCacheBinsPass());
+    $container->addCompilerPass(new CacheContextsPass());
     // Add the compiler pass for appending string translators.
     $container->addCompilerPass(new RegisterStringTranslatorsPass());
     // Add the compiler pass that will process the tagged breadcrumb builder
diff --git a/core/lib/Drupal/Core/Http/RequestCacheContexts.php b/core/lib/Drupal/Core/Http/RequestCacheContexts.php
new file mode 100644
index 0000000..fada2c7
--- /dev/null
+++ b/core/lib/Drupal/Core/Http/RequestCacheContexts.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Drupal\Core\Http;
+
+use Symfony\Component\HttpFoundation\Request;
+
+class RequestCacheContexts {
+
+  /**
+   * @param Symfony\Component\HttpFoundation\Request $request
+   *   The HTTP request object.
+   */
+  public function __construct(Request $request) {
+    $this->request = $request;
+  }
+
+  static function getCacheContexts() {
+    return array(
+      "http.request_path" => array(
+        "callback" => "getCurrentPath",
+        "label" => "Request path",
+      ),
+    );
+  }
+
+  /**
+   * @return string
+   *   The current path.
+   */
+  public function getCurrentPath() {
+    // @todo: Make this use the request.
+    global $base_root;
+    return $base_root . request_uri();
+  }
+
+}
diff --git a/core/modules/block/lib/Drupal/block/BlockBase.php b/core/modules/block/lib/Drupal/block/BlockBase.php
index 9d03d08..e17d295 100644
--- a/core/modules/block/lib/Drupal/block/BlockBase.php
+++ b/core/modules/block/lib/Drupal/block/BlockBase.php
@@ -62,6 +62,7 @@ protected function baseConfigurationDefaults() {
       'label_display' => BlockInterface::BLOCK_LABEL_VISIBLE,
       'cache' => array(
         'max_age' => 0,
+        'cache_contexts' => array(),
       ),
     );
   }
@@ -130,12 +131,27 @@ public function buildConfigurationForm(array $form, array &$form_state) {
     $period = array_map('format_interval', array_combine($period, $period));
     $period[0] = '<' . t('no caching') . '>';
     $period[\Drupal\Core\Cache\Cache::PERMANENT] = t('Forever');
+    $form['cache'] = array(
+      '#type' => 'fieldset',
+      '#title' => t('Cache'),
+    );
     $form['cache']['max_age'] = array(
       '#type' => 'select',
-      '#title' => t('Cache: Maximum age'),
+      '#title' => t('Maximum age'),
       '#description' => t('The maximum time a block can be cached.'),
       '#default_value' => $this->configuration['cache']['max_age'],
       '#options' => $period,
+      '#fieldset' => 'cache',
+    );
+    $cache_contexts = \Drupal::service("cache_contexts");
+    $form['cache']['cache_contexts'] = array(
+      '#type' => 'select',
+      '#multiple' => true,
+      '#title' => t('Keys'),
+      '#description' => t('Additional keys to vary the cache by.'),
+      '#default_value' => $this->configuration['cache']['cache_contexts'],
+      '#options' => $cache_contexts->getLabels(),
+      '#fieldset' => 'cache',
     );
     // Add plugin-specific settings for this block type.
     $form += $this->blockForm($form, $form_state);
@@ -256,4 +272,10 @@ public function isCacheable() {
     return $this->configuration['cache']['max_age'] > 0;
   }
 
+  /**
+   */
+  public function getCacheContexts() {
+    return $this->configuration['cache']['cache_contexts'];
+  }
+
 }
diff --git a/core/modules/block/lib/Drupal/block/BlockViewBuilder.php b/core/modules/block/lib/Drupal/block/BlockViewBuilder.php
index 6fe8abc..2554e7d 100644
--- a/core/modules/block/lib/Drupal/block/BlockViewBuilder.php
+++ b/core/modules/block/lib/Drupal/block/BlockViewBuilder.php
@@ -85,7 +85,11 @@ public function viewMultiple(array $entities = array(), $view_mode = 'full', $la
         $default_cache_keys = array('entity_view', 'block', $entity->id(), $entity->langcode);
         $max_age = $plugin->getCacheMaxAge();
         $build[$entity_id]['#cache'] += array(
-          'keys' => array_merge($default_cache_keys, $plugin->getCacheKeys()),
+          'keys' => array_merge(
+            $default_cache_keys,
+            $plugin->getCacheKeys(),
+            $plugin->getCacheContexts()
+          ),
           'bin' => $plugin->getCacheBin(),
           'expire' => ($max_age === Cache::PERMANENT) ? Cache::PERMANENT : REQUEST_TIME + $max_age,
         );
diff --git a/core/modules/forum/lib/Drupal/forum/Plugin/Block/ForumBlockBase.php b/core/modules/forum/lib/Drupal/forum/Plugin/Block/ForumBlockBase.php
index d088b23..972d2a8 100644
--- a/core/modules/forum/lib/Drupal/forum/Plugin/Block/ForumBlockBase.php
+++ b/core/modules/forum/lib/Drupal/forum/Plugin/Block/ForumBlockBase.php
@@ -9,7 +9,7 @@
 
 use Drupal\block\BlockBase;
 use Drupal\Core\Session\AccountInterface;
-use Drupal\Core\Cache\CacheableHelper;
+use Drupal\Core\Cache\Cache;
 
 /**
  * Provides a base class for Forum blocks.
@@ -84,8 +84,7 @@ public function blockSubmit($form, &$form_state) {
    * {@inheritdoc}
    */
   public function getCacheKeys() {
-    $cacheable_helper = new CacheableHelper;
-    return array($cacheable_helper->cacheKeyFromQuery($this->buildForumQuery()));
+    return array(Cache::keyFromQuery($this->buildForumQuery()));
   }
 
 }
diff --git a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php
index dc5b8da..89a859d 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php
@@ -124,9 +124,9 @@ public function buildConfigurationForm(array $form, array &$form_state) {
     $form = parent::buildConfigurationForm($form, $form_state);
 
     // The help block is never cacheable, because it is path-specific.
-    $form['cache']['max_age']['#disabled'] = TRUE;
+    $form['cache']['#disabled'] = TRUE;
+    $form['cache']['#description'] = t('This block is never cacheable, it is not configurable.');
     $form['cache']['max_age']['#value'] = 0;
-    $form['cache']['max_age']['#description'] = t('This block is never cacheable, it is not configurable.');
 
     return $form;
   }
diff --git a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemMainBlock.php b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemMainBlock.php
index b683373..666b515 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemMainBlock.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemMainBlock.php
@@ -35,9 +35,9 @@ public function buildConfigurationForm(array $form, array &$form_state) {
     $form = parent::buildConfigurationForm($form, $form_state);
 
     // The main content block is never cacheable, because it may be dynamic.
-    $form['cache']['max_age']['#disabled'] = TRUE;
+    $form['cache']['#disabled'] = TRUE;
+    $form['cache']['#description'] = t('This block is never cacheable, it is not configurable.');
     $form['cache']['max_age']['#value'] = 0;
-    $form['cache']['max_age']['#description'] = t('This block is never cacheable, it is not configurable.');
 
     return $form;
   }
diff --git a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemPoweredByBlock.php b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemPoweredByBlock.php
index 4b603bf..b0878f8 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemPoweredByBlock.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemPoweredByBlock.php
@@ -36,9 +36,9 @@ public function buildConfigurationForm(array $form, array &$form_state) {
 
     // The 'Powered by Drupal' block is permanently cacheable, because its
     // contents can never change.
-    $form['cache']['max_age']['#disabled'] = TRUE;
+    $form['cache']['#disabled'] = TRUE;
     $form['cache']['max_age']['#value'] = Cache::PERMANENT;
-    $form['cache']['max_age']['#description'] = t('This block is always cached forever, it is not configurable.');
+    $form['cache']['#description'] = t('This block is always cached forever, it is not configurable.');
 
     return $form;
   }
diff --git a/core/modules/user/lib/Drupal/user/CacheContexts.php b/core/modules/user/lib/Drupal/user/CacheContexts.php
new file mode 100644
index 0000000..8ee8789
--- /dev/null
+++ b/core/modules/user/lib/Drupal/user/CacheContexts.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace Drupal\user;
+
+use Drupal\Core\Session\AccountInterface;
+
+class CacheContexts {
+
+  /**
+   * @param \Drupal\Core\Session\AccountInterface $user
+   *   The current user.
+   */
+  public function __construct(AccountInterface $user) {
+    $this->user = $user;
+  }
+
+  static function getCacheContexts() {
+    return array(
+      "user.current_user" => array(
+        "callback" => "getCurrentUser",
+        "label" => "Current user id",
+      ),
+      "user.current_user_roles" => array(
+        "callback" => "getCurrentUserRoles",
+        "label" => "Current user's roles",
+      ),
+    );
+  }
+
+  public function getCurrentUser() {
+    return "u." . $this->user()->id();
+  }
+
+  public function getCurrentUserRoles() {
+    return 'r.' . implode(',', $this->user->getRoles());
+  }
+
+}
diff --git a/core/modules/user/user.services.yml b/core/modules/user/user.services.yml
index 23d8706..e444cf9 100644
--- a/core/modules/user/user.services.yml
+++ b/core/modules/user/user.services.yml
@@ -15,6 +15,11 @@ services:
     class: Drupal\user\Access\LoginStatusCheck
     tags:
       - { name: access_check, applies_to: _user_is_logged_in }
+  user.cache.contexts:
+    class: Drupal\user\CacheContexts
+    arguments: ['@current_user']
+    tags:
+      - { name: cache.context}
   user.data:
     class: Drupal\user\UserData
     arguments: ['@database']
diff --git a/core/tests/Drupal/Tests/Core/Cache/CacheContextsTest.php b/core/tests/Drupal/Tests/Core/Cache/CacheContextsTest.php
new file mode 100644
index 0000000..f1bc656
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Cache/CacheContextsTest.php
@@ -0,0 +1,81 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\Tests\Core\Cache\CacheContextsTest.
+ */
+
+namespace Drupal\Tests\Core\Cache;
+
+use Drupal\Core\Cache\CacheContexts;
+
+/**
+ * Fake cache context class.
+ */
+class SomeClass {
+  function someMethod() {
+    return "foo";
+  }
+}
+
+/**
+ * @group Cache
+ *
+ * @see \Drupal\Core\Cache\CacheContexts
+ */
+class CacheContextsTest extends \PHPUnit_Framework_TestCase {
+
+  public static function getInfo() {
+    return array(
+      'name' => 'CacheContext test',
+      'description' => 'Tests cache contexts.',
+      'group' => 'Cache',
+    );
+  }
+
+  public function testContextPlaceholdersAreReplaced() {
+    $container = $this->getMockContainer();
+    $container->expects($this->once())
+              ->method("get")
+              ->with("some_service")
+              ->will($this->returnValue(new SomeClass));
+
+    $cache_contexts = new CacheContexts($container, $this->getContextsFixture());
+
+    $new_keys = $cache_contexts->addContextsToKeys(
+      array("non-cache-context", "somemodule.some_context")
+    );
+
+    $expected = array("non-cache-context", "foo");
+    $this->assertEquals($expected, $new_keys);
+  }
+
+  public function testAvailableContextStrings() {
+    $cache_contexts = new CacheContexts($this->getMockContainer(), $this->getContextsFixture());
+    $contexts = $cache_contexts->getAll();
+    $this->assertEquals(array("somemodule.some_context"), $contexts);
+  }
+
+  public function testAvailableContextLabels() {
+    $cache_contexts = new CacheContexts($this->getMockContainer(), $this->getContextsFixture());
+    $labels = $cache_contexts->getLabels();
+    $expected = array("somemodule.some_context" => "Some label");
+    $this->assertEquals($expected, $labels);
+  }
+
+  protected function getContextsFixture() {
+    return array(
+      "somemodule.some_context" => array(
+        "service" => "some_service",
+        "callback" => "someMethod",
+        "label" => "Some label",
+      )
+    );
+  }
+
+  protected function getMockContainer() {
+    return $this->getMockBuilder('Drupal\Core\DependencyInjection\Container')
+                ->disableOriginalConstructor()
+                ->getMock();
+  }
+}