diff --git a/core/lib/Drupal/Component/Serialization/Yaml.php b/core/lib/Drupal/Component/Serialization/Yaml.php
index 5e104ba..3df8f84 100644
--- a/core/lib/Drupal/Component/Serialization/Yaml.php
+++ b/core/lib/Drupal/Component/Serialization/Yaml.php
@@ -7,42 +7,34 @@
 
 namespace Drupal\Component\Serialization;
 
-use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
-use Symfony\Component\Yaml\Parser;
-use Symfony\Component\Yaml\Dumper;
-
 /**
- * Default serialization for YAML using the Symfony component.
+ * YAML serialization implementation.
+ *
+ * Proxy implementation that will choose the best library based on availability.
  */
 class Yaml implements SerializationInterface {
 
   /**
+   * The YAML implementation to use.
+   *
+   * @var \Drupal\Component\Serialization\SerializationInterface
+   */
+  protected static $serializer;
+
+  /**
    * {@inheritdoc}
    */
   public static function encode($data) {
-    try {
-      $yaml = new Dumper();
-      $yaml->setIndentation(2);
-      return $yaml->dump($data, PHP_INT_MAX, 0, TRUE, FALSE);
-    }
-    catch (\Exception $e) {
-      throw new InvalidDataTypeException($e->getMessage(), $e->getCode(), $e);
-    }
+    $serializer = static::getSerializer();
+    return $serializer::encode($data);
   }
 
   /**
    * {@inheritdoc}
    */
   public static function decode($raw) {
-    try {
-      $yaml = new Parser();
-      // Make sure we have a single trailing newline. A very simple config like
-      // 'foo: bar' with no newline will fail to parse otherwise.
-      return $yaml->parse($raw, TRUE, FALSE);
-    }
-    catch (\Exception $e) {
-      throw new InvalidDataTypeException($e->getMessage(), $e->getCode(), $e);
-    }
+    $serializer = static::getSerializer();
+    return $serializer::decode($raw);
   }
 
   /**
@@ -52,4 +44,22 @@ public static function getFileExtension() {
     return 'yml';
   }
 
+  /**
+   * Determines the optimal implementation to use for encoding and parsing YAML.
+   */
+  protected static function getSerializer() {
+
+    if (!isset(static::$serializer)) {
+      // Use the PECL Yaml extension if it is available.
+      if (extension_loaded('yaml')) {
+        static::$serializer = '\Drupal\Component\Serialization\YamlPecl';
+      }
+      else {
+        // Otherwise, fallback to the Symfony implementation.
+        static::$serializer = '\Drupal\Component\Serialization\YamlSymfony';
+      }
+    }
+    return static::$serializer;
+  }
+
 }
diff --git a/core/lib/Drupal/Component/Serialization/YamlPecl.php b/core/lib/Drupal/Component/Serialization/YamlPecl.php
new file mode 100644
index 0000000..0fd833c
--- /dev/null
+++ b/core/lib/Drupal/Component/Serialization/YamlPecl.php
@@ -0,0 +1,99 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Serialization\YamlPecl.
+ */
+
+namespace Drupal\Component\Serialization;
+
+use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
+
+/**
+ * Default serialization for YAML using the PECL extension.
+ */
+class YamlPecl implements SerializationInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function encode($data) {
+    static $init;
+    if (!isset($init)) {
+      ini_set('yaml.output_indent', 2);
+      // Do not break lines at 80 characters.
+      ini_set('yaml.output_width', -1);
+      $init = TRUE;
+    }
+    return yaml_emit($data, YAML_UTF8_ENCODING, YAML_LN_BREAK);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function decode($raw) {
+    // yaml_parse() will error with an empty value.
+    if (!trim($raw)) {
+      return NULL;
+    }
+    // @todo Use ErrorExceptions when https://drupal.org/node/1247666 is in.
+    // yaml_parse() will throw errors instead of raising an exception. Until
+    // such time as Drupal supports native PHP ErrorExceptions as the error
+    // handler, we need to temporarily set the error handler as ::errorHandler()
+    // and then restore it after decoding has occurred. This allows us to turn
+    // parsing errors into a throwable exception.
+    // @see Drupal\Component\Serialization\Exception\InvalidDataTypeException
+    // @see http://php.net/manual/en/class.errorexception.php
+    set_error_handler([__CLASS__, 'errorHandler']);
+    $ndocs = 0;
+    $data = yaml_parse($raw, 0, $ndocs, [
+      YAML_BOOL_TAG => '\Drupal\Component\Serialization\YamlPecl::applyBooleanCallbacks',
+    ]);
+    restore_error_handler();
+    return $data;
+  }
+
+  /**
+   * Temporary error handler for YamlPecl::decode().
+   */
+  public static function errorHandler($severity, $message, $file, $line) {
+    restore_error_handler();
+    throw new InvalidDataTypeException($message, $severity);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getFileExtension() {
+    return 'yml';
+  }
+
+  /**
+   * Applies callbacks after parsing to ignore 1.1 style booleans.
+   *
+   * @param mixed $value
+   *   Value from YAML file.
+   * @param string $tag
+   *   Tag that triggered the callback.
+   * @param int $flags
+   *   Scalar entity style flags.
+   *
+   * @return string|bool
+   *   FALSE, false, TRUE and true are returned as booleans, everything else is
+   *   returned as a string.
+   */
+  public static function applyBooleanCallbacks($value, $tag, $flags) {
+    // YAML 1.1 spec dictates that 'Y', 'N', 'y' and 'n' are booleans, we want
+    // the 1.2 behaviour so we only case 'false', 'FALSE', 'true' OR 'TRUE' as
+    // booleans.
+    if (!in_array(strtolower($value), ['false', 'true'], TRUE)) {
+      return $value;
+    }
+    $map = [
+      'false' => FALSE,
+      'true' => TRUE,
+    ];
+    return $map[strtolower($value)];
+  }
+
+}
diff --git a/core/lib/Drupal/Component/Serialization/Yaml.php b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
similarity index 91%
copy from core/lib/Drupal/Component/Serialization/Yaml.php
copy to core/lib/Drupal/Component/Serialization/YamlSymfony.php
index 5e104ba..4ca5e25 100644
--- a/core/lib/Drupal/Component/Serialization/Yaml.php
+++ b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Component\Serialization\Yaml.
+ * Contains \Drupal\Component\Serialization\YamlSymfony.
  */
 
 namespace Drupal\Component\Serialization;
@@ -14,7 +14,7 @@
 /**
  * Default serialization for YAML using the Symfony component.
  */
-class Yaml implements SerializationInterface {
+class YamlSymfony implements SerializationInterface {
 
   /**
    * {@inheritdoc}
diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
index 427640f..5c14299 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
@@ -13,9 +13,9 @@
 use Drupal\Core\Asset\Exception\LibraryDefinitionMissingLicenseException;
 use Drupal\Core\Extension\Extension;
 use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Serialization\Yaml;
 use Drupal\Core\Theme\ThemeManagerInterface;
 use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
-use Drupal\Component\Serialization\Yaml;
 use Drupal\Component\Utility\NestedArray;
 
 /**
diff --git a/core/lib/Drupal/Core/Config/ConfigManager.php b/core/lib/Drupal/Core/Config/ConfigManager.php
index e5b471d..c495c80 100644
--- a/core/lib/Drupal/Core/Config/ConfigManager.php
+++ b/core/lib/Drupal/Core/Config/ConfigManager.php
@@ -8,7 +8,7 @@
 namespace Drupal\Core\Config;
 
 use Drupal\Component\Diff\Diff;
-use Drupal\Component\Serialization\Yaml;
+use Drupal\Core\Serialization\Yaml;
 use Drupal\Core\Config\Entity\ConfigDependencyManager;
 use Drupal\Core\Config\Entity\ConfigEntityInterface;
 use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
diff --git a/core/lib/Drupal/Core/Config/FileStorage.php b/core/lib/Drupal/Core/Config/FileStorage.php
index aaac182..d486551 100644
--- a/core/lib/Drupal/Core/Config/FileStorage.php
+++ b/core/lib/Drupal/Core/Config/FileStorage.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Config;
 
-use Drupal\Component\Serialization\Yaml;
+use Drupal\Core\Serialization\Yaml;
 use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
 
 /**
diff --git a/core/lib/Drupal/Core/DependencyInjection/YamlFileLoader.php b/core/lib/Drupal/Core/DependencyInjection/YamlFileLoader.php
index 4c7fea9..a8dd98f 100644
--- a/core/lib/Drupal/Core/DependencyInjection/YamlFileLoader.php
+++ b/core/lib/Drupal/Core/DependencyInjection/YamlFileLoader.php
@@ -7,8 +7,8 @@
 
 namespace Drupal\Core\DependencyInjection;
 
+use Drupal\Core\Serialization\Yaml;
 use Drupal\Component\FileCache\FileCacheFactory;
-use Drupal\Component\Serialization\Yaml;
 use Symfony\Component\DependencyInjection\Alias;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Definition;
diff --git a/core/lib/Drupal/Core/Discovery/YamlDiscovery.php b/core/lib/Drupal/Core/Discovery/YamlDiscovery.php
new file mode 100644
index 0000000..bac6219
--- /dev/null
+++ b/core/lib/Drupal/Core/Discovery/YamlDiscovery.php
@@ -0,0 +1,30 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Discovery\YamlDiscovery.
+ */
+
+namespace Drupal\Core\Discovery;
+
+use Drupal\Core\Serialization\Yaml;
+use Drupal\Component\Discovery\YamlDiscovery as ComponentYamlDiscovery;
+
+/**
+ * Provides discovery for YAML files within a given set of directories.
+ */
+class YamlDiscovery extends ComponentYamlDiscovery {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function findAll() {
+    $all = array();
+    foreach ($this->findFiles() as $provider => $file) {
+      $all[$provider] = Yaml::decode(file_get_contents($file));
+    }
+
+    return $all;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Extension/InfoParserDynamic.php b/core/lib/Drupal/Core/Extension/InfoParserDynamic.php
index 64e4941..ec68ecd 100644
--- a/core/lib/Drupal/Core/Extension/InfoParserDynamic.php
+++ b/core/lib/Drupal/Core/Extension/InfoParserDynamic.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Extension;
 
-use Drupal\Component\Serialization\Yaml;
+use Drupal\Core\Serialization\Yaml;
 use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
 
 /**
diff --git a/core/lib/Drupal/Core/Extension/ModuleInstaller.php b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
index 92bdb80..5d8abf1 100644
--- a/core/lib/Drupal/Core/Extension/ModuleInstaller.php
+++ b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Extension;
 
-use Drupal\Component\Serialization\Yaml;
+use Drupal\Core\Serialization\Yaml;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\DrupalKernelInterface;
diff --git a/core/lib/Drupal/Core/Plugin/Discovery/YamlDiscovery.php b/core/lib/Drupal/Core/Plugin/Discovery/YamlDiscovery.php
index 97ea374..285d3b7 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/YamlDiscovery.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/YamlDiscovery.php
@@ -8,7 +8,7 @@
 namespace Drupal\Core\Plugin\Discovery;
 
 use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
-use Drupal\Component\Discovery\YamlDiscovery as ComponentYamlDiscovery;
+use Drupal\Core\Discovery\YamlDiscovery as CoreYamlDiscovery;
 use Drupal\Component\Plugin\Discovery\DiscoveryTrait;
 use Drupal\Core\StringTranslation\TranslatableMarkup;
 
@@ -53,7 +53,7 @@ class YamlDiscovery implements DiscoveryInterface {
    *   An array of directories to scan.
    */
   function __construct($name, array $directories) {
-    $this->discovery = new ComponentYamlDiscovery($name, $directories);
+    $this->discovery = new CoreYamlDiscovery($name, $directories);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Serialization/Yaml.php b/core/lib/Drupal/Core/Serialization/Yaml.php
new file mode 100644
index 0000000..03effff
--- /dev/null
+++ b/core/lib/Drupal/Core/Serialization/Yaml.php
@@ -0,0 +1,33 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Serialization\Yaml.
+ */
+
+namespace Drupal\Core\Serialization;
+
+use Drupal\Core\Site\Settings;
+use Drupal\Component\Serialization\Yaml as ComponentYaml;
+
+/**
+ * YAML serialization implementation.
+ *
+ * Allow settings to override the YAML implementation resolution.
+ */
+class Yaml extends ComponentYaml {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static function getSerializer() {
+    // Allow settings.php to override the YAML serializer.
+    if (!isset(static::$serializer) &&
+      $class = Settings::get('yaml_parser_class')) {
+
+      static::$serializer = $class;
+    }
+    return parent::getSerializer();
+  }
+
+}
diff --git a/core/modules/config/src/Tests/ConfigDiffTest.php b/core/modules/config/src/Tests/ConfigDiffTest.php
index 10f6902..12b948d 100644
--- a/core/modules/config/src/Tests/ConfigDiffTest.php
+++ b/core/modules/config/src/Tests/ConfigDiffTest.php
@@ -52,9 +52,9 @@ function testDiff() {
     // Verify that the diff reflects a change.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name);
     $edits = $diff->getEdits();
-    $this->assertEqual($edits[0]->type, 'change', 'The first item in the diff is a change.');
-    $this->assertEqual($edits[0]->orig[0], $change_key . ': ' . $original_data[$change_key], format_string("The active value for key '%change_key' is '%original_data'.", array('%change_key' => $change_key, '%original_data' => $original_data[$change_key])));
-    $this->assertEqual($edits[0]->closing[0], $change_key . ': ' . $change_data, format_string("The staging value for key '%change_key' is '%change_data'.", array('%change_key' => $change_key, '%change_data' => $change_data)));
+    $this->assertYamlEdit($edits, $change_key, 'change',
+      [$change_key . ': ' . $original_data[$change_key]],
+      [$change_key . ': ' . $change_data]);
 
     // Reset data back to original, and remove a key
     $staging_data = $original_data;
@@ -64,10 +64,11 @@ function testDiff() {
     // Verify that the diff reflects a removed key.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name);
     $edits = $diff->getEdits();
-    $this->assertEqual($edits[0]->type, 'copy', 'The first item in the diff is a copy.');
-    $this->assertEqual($edits[1]->type, 'delete', 'The second item in the diff is a delete.');
-    $this->assertEqual($edits[1]->orig[0], $remove_key . ': ' . $original_data[$remove_key], format_string("The active value for key '%remove_key' is '%original_data'.", array('%remove_key' => $remove_key, '%original_data' => $original_data[$remove_key])));
-    $this->assertFalse($edits[1]->closing, format_string("The key '%remove_key' does not exist in staging.", array('%remove_key' => $remove_key)));
+    $this->assertYamlEdit($edits, $change_key, 'copy');
+    $this->assertYamlEdit($edits, $remove_key, 'delete',
+      [$remove_key . ': ' . $original_data[$remove_key]],
+      FALSE
+    );
 
     // Reset data back to original and add a key
     $staging_data = $original_data;
@@ -77,10 +78,8 @@ function testDiff() {
     // Verify that the diff reflects an added key.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name);
     $edits = $diff->getEdits();
-    $this->assertEqual($edits[0]->type, 'copy', 'The first item in the diff is a copy.');
-    $this->assertEqual($edits[1]->type, 'add', 'The second item in the diff is an add.');
-    $this->assertFalse($edits[1]->orig, format_string("The key '%add_key' does not exist in active.", array('%add_key' => $add_key)));
-    $this->assertEqual($edits[1]->closing[0], $add_key . ': ' . $add_data, format_string("The staging value for key '%add_key' is '%add_data'.", array('%add_key' => $add_key, '%add_data' => $add_data)));
+    $this->assertYamlEdit($edits, $change_key, 'copy');
+    $this->assertYamlEdit($edits, $add_key, 'add', FALSE, [$add_key . ': ' . $add_data]);
 
     // Test diffing a renamed config entity.
     $test_entity_id = $this->randomMachineName();
@@ -105,10 +104,11 @@ function testDiff() {
 
     $diff = \Drupal::service('config.manager')->diff($active, $staging, 'config_test.dynamic.' . $new_test_entity_id, $config_name);
     $edits = $diff->getEdits();
-    $this->assertEqual($edits[0]->type, 'copy',  'The first item in the diff is a copy.');
-    $this->assertEqual($edits[1]->type, 'change',  'The second item in the diff is a change.');
-    $this->assertEqual($edits[1]->orig, array('id: ' . $new_test_entity_id));
-    $this->assertEqual($edits[1]->closing, array('id: ' . $test_entity_id));
+    $this->assertYamlEdit($edits, 'uuid', 'copy');
+    $this->assertYamlEdit($edits, 'id', 'change',
+      ['id: ' . $new_test_entity_id],
+      ['id: ' . $test_entity_id]);
+    $this->assertYamlEdit($edits, 'label', 'copy');
     $this->assertEqual($edits[2]->type, 'copy',  'The third item in the diff is a copy.');
     $this->assertEqual(count($edits), 3, 'There are three items in the diff.');
   }
@@ -141,10 +141,54 @@ function testCollectionDiff() {
     // Test that the differences are detected when diffing the collection.
     $diff = \Drupal::service('config.manager')->diff($active, $staging, $config_name, NULL, 'test');
     $edits = $diff->getEdits();
-    $this->assertEqual($edits[0]->type, 'change',  'The second item in the diff is a copy.');
-    $this->assertEqual($edits[0]->orig, array('foo: bar'));
-    $this->assertEqual($edits[0]->closing, array('foo: baz'));
-    $this->assertEqual($edits[1]->type, 'copy',  'The second item in the diff is a copy.');
+    $this->assertYamlEdit($edits, 'foo', 'change', ['foo: bar'], ['foo: baz']);
+  }
+
+  /**
+   * Helper method to test that an edit is found in a diff'd yaml file.
+   *
+   * @param array $edits
+   *   A list of edits.
+   * @param $field
+   *   The field key that is being asserted.
+   * @param $type
+   *   The type of edit that is being asserted.
+   * @param mixed $orig
+   *   (optional) The original value of of the edit. If not supplied, assertion is skipped.
+   * @param mixed $closing
+   *   (optional) The closing value of of the edit. If not supplied, assertion is skipped.
+   */
+  protected function assertYamlEdit(array $edits, $field, $type, $orig = null, $closing = null) {
+    $match = FALSE;
+    foreach ($edits as $edit) {
+      // Choose which section to search for the field.
+      $haystack = $type == 'add' ? $edit->closing : $edit->orig;
+      // Look through each line and try and find the key.
+      if (is_array($haystack)) {
+        foreach ($haystack as $item) {
+          if (strpos($item, $field . ':') === 0) {
+            $match = TRUE;
+            // Assert that the edit is of the type specified.
+            $this->assertEqual($edit->type, $type, "The $field item in the diff is a $type");
+            // If an original value was given, assert that it matches.
+            if (isset($orig)) {
+              $this->assertIdentical($edit->orig, $orig, "The original value for key '$field' is correct.");
+            }
+            // If a closing value was given, assert that it matches.
+            if (isset($closing)) {
+              $this->assertIdentical($edit->closing, $closing, "The closing value for key '$field' is correct.");
+            }
+            // Break out of the search entirely.
+            break 2;
+          }
+        }
+      }
+    }
+
+    // If we didn't match anything, fail.
+    if (!$match) {
+      $this->fail("$field edit was not matched");
+    }
   }
 
 }
diff --git a/core/modules/config/src/Tests/ConfigSingleImportExportTest.php b/core/modules/config/src/Tests/ConfigSingleImportExportTest.php
index 7b3336d..922f113 100644
--- a/core/modules/config/src/Tests/ConfigSingleImportExportTest.php
+++ b/core/modules/config/src/Tests/ConfigSingleImportExportTest.php
@@ -179,8 +179,8 @@ public function testExport() {
     $this->assertFieldByXPath('//select[@name="config_name"]//option[@selected="selected"]', t('Fallback date format'), 'The fallback date format config entity is selected when specified in the URL.');
 
     $fallback_date = \Drupal::entityManager()->getStorage('date_format')->load('fallback');
-    $data = Yaml::encode($fallback_date->toArray());
-    $this->assertFieldByXPath('//textarea[@name="export"]', $data, 'The fallback date format config entity export code is displayed.');
+    $yaml_text = (string) $this->xpath('//textarea[@name="export"]')[0];
+    $this->assertEqual(Yaml::decode($yaml_text), $fallback_date->toArray(), 'The fallback date format config entity export code is displayed.');
   }
 
 }
diff --git a/core/modules/image/migration_templates/d6_imagecache_presets.yml b/core/modules/image/migration_templates/d6_imagecache_presets.yml
index e4780a9..c3ec46f 100644
--- a/core/modules/image/migration_templates/d6_imagecache_presets.yml
+++ b/core/modules/image/migration_templates/d6_imagecache_presets.yml
@@ -18,7 +18,7 @@ process:
   effects:
     plugin: d6_imagecache_actions
     source:
-      - '@plugin'
+      - "@plugin"
       - data
 destination:
   plugin: entity:image_style
diff --git a/core/modules/system/src/Tests/Installer/StandardInstallerTest.php b/core/modules/system/src/Tests/Installer/StandardInstallerTest.php
index 184e07b..8c7d123 100644
--- a/core/modules/system/src/Tests/Installer/StandardInstallerTest.php
+++ b/core/modules/system/src/Tests/Installer/StandardInstallerTest.php
@@ -47,15 +47,15 @@ public function testStandardConfig() {
     $skipped_config = [];
     // \Drupal\simpletest\WebTestBase::installParameters() uses
     // simpletest@example.com as mail address.
-    $skipped_config['contact.form.feedback'][] = ' - simpletest@example.com';
+    $skipped_config['contact.form.feedback'][] = '- simpletest@example.com';
     // \Drupal\filter\Entity\FilterFormat::toArray() drops the roles of filter
     // formats.
     $skipped_config['filter.format.basic_html'][] = 'roles:';
-    $skipped_config['filter.format.basic_html'][] = ' - authenticated';
+    $skipped_config['filter.format.basic_html'][] = '- authenticated';
     $skipped_config['filter.format.full_html'][] = 'roles:';
-    $skipped_config['filter.format.full_html'][] = ' - administrator';
+    $skipped_config['filter.format.full_html'][] = '- administrator';
     $skipped_config['filter.format.restricted_html'][] = 'roles:';
-    $skipped_config['filter.format.restricted_html'][] = ' - anonymous';
+    $skipped_config['filter.format.restricted_html'][] = '- anonymous';
 
     $this->assertInstalledConfig($skipped_config);
   }
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.services.yml b/core/modules/system/tests/modules/theme_test/theme_test.services.yml
index 482c219..66d5607 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.services.yml
+++ b/core/modules/system/tests/modules/theme_test/theme_test.services.yml
@@ -1,7 +1,7 @@
 services:
   theme_test.subscriber:
     class: Drupal\theme_test\EventSubscriber\ThemeTestSubscriber
-    arguments: [@current_route_match, @renderer]
+    arguments: ["@current_route_match", "@renderer"]
     tags:
       - { name: event_subscriber }
 
diff --git a/core/modules/views/tests/modules/views_test_config/test_views/views.view.test_group_rows.yml b/core/modules/views/tests/modules/views_test_config/test_views/views.view.test_group_rows.yml
index 2c34841..294e2fd 100644
--- a/core/modules/views/tests/modules/views_test_config/test_views/views.view.test_group_rows.yml
+++ b/core/modules/views/tests/modules/views_test_config/test_views/views.view.test_group_rows.yml
@@ -7,7 +7,6 @@ dependencies:
     - user
   config:
     - field.storage.node.field_views_testing_group_rows
-  module:
 id: test_group_rows
 label: test_group_rows
 module: views
diff --git a/core/profiles/standard/config/install/core.entity_view_display.node.article.default.yml b/core/profiles/standard/config/install/core.entity_view_display.node.article.default.yml
index e0d3782..a35424e 100644
--- a/core/profiles/standard/config/install/core.entity_view_display.node.article.default.yml
+++ b/core/profiles/standard/config/install/core.entity_view_display.node.article.default.yml
@@ -45,13 +45,6 @@ content:
     settings:
       link: true
     third_party_settings: {  }
-  comment:
-    label: above
-    type: comment_default
-    weight: 110
-    settings:
-      pager_id: 0
-    third_party_settings: {  }
   links:
     weight: 100
 hidden:
diff --git a/core/tests/Drupal/Tests/Component/Serialization/YamlPeclTest.php b/core/tests/Drupal/Tests/Component/Serialization/YamlPeclTest.php
new file mode 100644
index 0000000..5d94c91
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/Serialization/YamlPeclTest.php
@@ -0,0 +1,87 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Component\Serialization\YamlPeclTest.
+ */
+
+namespace Drupal\Tests\Component\Serialization;
+
+use Drupal\Component\Serialization\YamlPecl;
+
+/**
+ * Test the YamlPecl serialization implementation.
+ *
+ * @group Drupal
+ * @group Serialization
+ * @coversDefaultClass \Drupal\Component\Serialization\YamlPecl
+ * @requires extension yaml
+ */
+class YamlPeclTest extends YamlTestBase {
+
+  /**
+   * Tests encoding and decoding basic data structures.
+   *
+   * @covers ::encode
+   * @covers ::decode
+   * @dataProvider providerEncodeDecodeTests
+   */
+  public function testEncodeDecode($data) {
+    $this->assertEquals($data, YamlPecl::decode(YamlPecl::encode($data)));
+  }
+
+  /**
+   * Tests decoding YAML node anchors.
+   *
+   * @covers ::decode
+   * @dataProvider providerDecodeTests
+   */
+  public function testDecode($string, $data) {
+    $this->assertEquals($data, YamlPecl::decode($string));
+  }
+
+  /**
+   * Tests our encode settings.
+   *
+   * @covers ::encode
+   */
+  public function testEncode() {
+    $this->assertEquals('---
+foo:
+  bar: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus sapien ex, venenatis vitae nisi eu, posuere luctus dolor. Nullam convallis
+...
+', YamlPecl::encode(['foo' => ['bar' => 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus sapien ex, venenatis vitae nisi eu, posuere luctus dolor. Nullam convallis']]));
+  }
+
+  /**
+   * Test yaml boolean callback.
+   *
+   * @covers ::applyBooleanCallbacks
+   * @dataProvider providerBoolTest
+   * @param string $string
+   *   String value for the yaml boolean.
+   * @param string|bool $expected
+   *   The expected return
+   */
+  public function testApplyBooleanCallbacks($string, $expected) {
+    $this->assertEquals($expected, YamlPecl::applyBooleanCallbacks($string, 'bool', NULL));
+  }
+
+  /**
+   * @covers ::getFileExtension
+   */
+  public function testGetFileExtension() {
+    $this->assertEquals('yml', YamlPecl::getFileExtension());
+  }
+
+  /**
+   * Invalid yaml throws exception.
+   *
+   * @covers ::errorHandler
+   * @expectedException \Drupal\Component\Serialization\Exception\InvalidDataTypeException
+   */
+  public function testError() {
+    YamlPecl::decode('foo: [ads');
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Component/Serialization/YamlSymfonyTest.php b/core/tests/Drupal/Tests/Component/Serialization/YamlSymfonyTest.php
new file mode 100644
index 0000000..cafe3be
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/Serialization/YamlSymfonyTest.php
@@ -0,0 +1,71 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Component\Serialization\YamlSymfonyTest.
+ */
+
+namespace Drupal\Tests\Component\Serialization;
+
+use Drupal\Component\Serialization\YamlSymfony;
+
+/**
+ * Test the YamlSymfony serialization implementation.
+ *
+ * @group Drupal
+ * @group Serialization
+ * @coversDefaultClass \Drupal\Component\Serialization\YamlSymfony
+ * @requires extension yaml
+ */
+class YamlSymfonyTest extends YamlTestBase {
+
+  /**
+   * Tests encoding and decoding basic data structures.
+   *
+   * @covers ::encode
+   * @covers ::decode
+   * @dataProvider providerEncodeDecodeTests
+   */
+  public function testEncodeDecode($data) {
+    $this->assertEquals($data, YamlSymfony::decode(YamlSymfony::encode($data)));
+  }
+
+  /**
+   * Tests decoding YAML node anchors.
+   *
+   * @covers ::decode
+   * @dataProvider providerDecodeTests
+   */
+  public function testDecode($string, $data) {
+    $this->assertEquals($data, YamlSymfony::decode($string));
+  }
+
+  /**
+   * Tests our encode settings.
+   *
+   * @covers ::encode
+   */
+  public function testEncode() {
+    $this->assertEquals('foo:
+  bar: \'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus sapien ex, venenatis vitae nisi eu, posuere luctus dolor. Nullam convallis\'
+', YamlSymfony::encode(['foo' => ['bar' => 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus sapien ex, venenatis vitae nisi eu, posuere luctus dolor. Nullam convallis']]));
+  }
+
+  /**
+   * @covers ::getFileExtension
+   */
+  public function testGetFileExtension() {
+    $this->assertEquals('yml', YamlSymfony::getFileExtension());
+  }
+
+  /**
+   * Invalid yaml throws exception.
+   *
+   * @covers ::decode
+   * @expectedException \Drupal\Component\Serialization\Exception\InvalidDataTypeException
+   */
+  public function testError() {
+    YamlSymfony::decode('foo: [ads');
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Component/Serialization/YamlTest.php b/core/tests/Drupal/Tests/Component/Serialization/YamlTest.php
index 94269e6..972fa31 100644
--- a/core/tests/Drupal/Tests/Component/Serialization/YamlTest.php
+++ b/core/tests/Drupal/Tests/Component/Serialization/YamlTest.php
@@ -7,7 +7,11 @@
 
 namespace Drupal\Tests\Component\Serialization;
 
+use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
+use Drupal\Component\Serialization\SerializationInterface;
 use Drupal\Component\Serialization\Yaml;
+use Drupal\Component\Serialization\YamlPecl;
+use Drupal\Component\Serialization\YamlSymfony;
 use Drupal\Tests\UnitTestCase;
 
 /**
@@ -20,44 +24,118 @@ class YamlTest extends UnitTestCase {
    * @covers ::decode
    */
   public function testDecode() {
-    // Test that files without line break endings are properly interpreted.
-    $yaml = 'foo: bar';
-    $expected = array(
-      'foo' => 'bar',
-    );
-    $this->assertSame($expected, Yaml::decode($yaml));
-    $yaml .= "\n";
-    $this->assertSame($expected, Yaml::decode($yaml));
-    $yaml .= "\n";
-    $this->assertSame($expected, Yaml::decode($yaml));
-
-    $yaml = "{}\n";
-    $expected = array();
-    $this->assertSame($expected, Yaml::decode($yaml));
-
-    $yaml = '';
-    $this->assertNULL(Yaml::decode($yaml));
-    $yaml .= "\n";
-    $this->assertNULL(Yaml::decode($yaml));
-    $yaml .= "\n";
-    $this->assertNULL(Yaml::decode($yaml));
+    $stub = $this->getMockBuilder('\stdClass')
+      ->setMethods(['encode', 'decode', 'getFileExtension'])
+      ->getMock();
+    $stub
+      ->expects($this->once())
+      ->method('decode');
+    YamlParserProxy::setMock($stub);
+    YamlStub::decode('test');
   }
 
   /**
    * @covers ::encode
    */
   public function testEncode() {
-    $decoded = array(
-      'foo' => 'bar',
-    );
-    $this->assertSame('foo: bar' . "\n", Yaml::encode($decoded));
+    $stub = $this->getMockBuilder('\stdClass')
+      ->setMethods(['encode', 'decode', 'getFileExtension'])
+      ->getMock();
+    $stub
+      ->expects($this->once())
+      ->method('encode');
+    YamlParserProxy::setMock($stub);
+    YamlStub::encode([]);
   }
 
   /**
    * @covers ::getFileExtension
    */
   public function testGetFileExtension() {
-    $this->assertEquals('yml', Yaml::getFileExtension());
+    $stub = $this->getMockBuilder('\stdClass')
+      ->setMethods(['encode', 'decode', 'getFileExtension'])
+      ->getMock();
+    $stub
+      ->expects($this->never())
+      ->method('getFileExtension');
+    YamlParserProxy::setMock($stub);
+    $this->assertEquals('yml', YamlStub::getFileExtension());
+  }
+
+  /**
+   * Tests all YAML files are decoded in the same way with both Symfony and PECL.
+   *
+   * This tests is a little bit slow but it tests that we don't have any bugs
+   * in our YAML that might not be decoded correctly in on of our
+   * implementations.
+   *
+   * @todo This should exist as an integration test not part of our unit tests.
+   *
+   * @requires extension yaml
+   * @dataProvider providerYamlFilesInCore
+   */
+  public function testYamlFiles($file) {
+    $data = file_get_contents($file);
+    try {
+      $this->assertEquals(YamlSymfony::decode($data), YamlPecl::decode($data), $file);
+    }
+    catch (InvalidDataTypeException $e) {
+      // Provide file context to the failure so the exception message is useful.
+      $this->fail("Exception thrown parsing $file:\n" . $e->getMessage());
+    }
+  }
+
+  /**
+   * Data provider that lists all YAML files in core.
+   */
+  public function providerYamlFilesInCore() {
+    $files = [];
+    $dirs = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator(__DIR__ . '/../../../../../', \RecursiveDirectoryIterator::FOLLOW_SYMLINKS));
+    foreach ($dirs as $dir) {
+      $pathname = $dir->getPathname();
+      // Exclude vendor.
+      if ($dir->getExtension() == 'yml' && strpos($pathname, '/../../../../../vendor') === FALSE) {
+        if (strpos($dir->getRealPath(), 'invalid_file') !== FALSE) {
+          // There are some intentionally invalid files provided for testing
+          // library API behaviours, ignore them.
+          continue;
+        }
+        $files[] = array($dir->getRealPath());
+      }
+    }
+    return $files;
+  }
+}
+
+class YamlStub extends Yaml {
+
+  public static function getSerializer() {
+    return '\Drupal\Tests\Component\Serialization\YamlParserProxy';
+  }
+
+}
+
+class YamlParserProxy implements SerializationInterface {
+
+  /**
+   * @var \Drupal\Component\Serialization\SerializationInterface
+   */
+  static $mock;
+
+  public static function setMock($mock) {
+    static::$mock = $mock;
+  }
+
+  public static function encode($data) {
+    return static::$mock->encode($data);
+  }
+
+  public static function decode($raw) {
+    return static::$mock->decode($raw);
+  }
+
+  public static function getFileExtension() {
+    return static::$mock->getFileExtension();
   }
 
 }
diff --git a/core/tests/Drupal/Tests/Component/Serialization/YamlTestBase.php b/core/tests/Drupal/Tests/Component/Serialization/YamlTestBase.php
new file mode 100644
index 0000000..8a4614b
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/Serialization/YamlTestBase.php
@@ -0,0 +1,104 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Component\Serialization\YamlPeclTest.
+ */
+
+namespace Drupal\Tests\Component\Serialization;
+
+/**
+ * Provides standard data to validate different YAML implementations.
+ */
+abstract class YamlTestBase extends \PHPUnit_Framework_TestCase {
+
+  /**
+   * Some data that should be able to be serialized.
+   */
+  public function providerEncodeDecodeTests() {
+    return [
+      [
+        'foo' => 'bar',
+        'id' => 'schnitzel',
+        'ponies' => ['nope', 'thanks'],
+        'how' => [
+          'about' => 'if',
+          'i' => 'ask',
+          'nicely',
+        ],
+        'the' => [
+          'answer' => [
+            'still' => 'would',
+            'be' => 'Y',
+          ],
+        ],
+        'how_many_times' => 123,
+        'should_i_ask' => FALSE,
+        1,
+        FALSE,
+        [1, FALSE],
+        [10],
+        [0 => '123456'],
+      ],
+      [NULL]
+    ];
+  }
+
+  /**
+   * Some data that should be able to be de-serialized.
+   */
+  public function providerDecodeTests() {
+    $data = [
+      // NULL files.
+      ['', NULL],
+      ["\n", NULL],
+      ["---\n...\n", NULL],
+
+      // Node anchors.
+      [
+        "
+jquery.ui:
+  version: &jquery_ui 1.10.2
+
+jquery.ui.accordion:
+  version: *jquery_ui
+",
+        [
+          'jquery.ui' => [
+            'version' => '1.10.2',
+          ],
+          'jquery.ui.accordion' => [
+            'version' => '1.10.2',
+          ],
+        ],
+      ],
+    ];
+
+    // 1.2 Bool values.
+    foreach ($this->providerBoolTest() as $test) {
+      $data[] = ['bool: ' . $test[0], ['bool' => $test[1]]];
+    }
+    $data = array_merge($data, $this->providerBoolTest());
+
+    return $data;
+  }
+
+  /**
+   * Test different boolean serialization and de-serialization.
+   */
+  public function providerBoolTest() {
+    return [
+      ['true', TRUE],
+      ['TRUE', TRUE],
+      ['True', TRUE],
+      ['y', 'y'],
+      ['Y', 'Y'],
+      ['false', FALSE],
+      ['FALSE', FALSE],
+      ['False', FALSE],
+      ['n', 'n'],
+      ['N', 'N'],
+    ];
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
index 2f5ed21..99879d9 100644
--- a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
@@ -225,34 +225,6 @@ public function testVersion() {
     $this->assertEquals(\Drupal::VERSION, $libraries['core-versioned']['js'][0]['version']);
   }
 
-  /**
-   * Tests the version property with ISO dates.
-   *
-   * We want to make sure that versions defined in the YAML file are the same
-   * versions that are parsed.
-   *
-   * For example, ISO dates are converted into UNIX time by the YAML parser.
-   *
-   * @covers ::buildByExtension
-   */
-  public function testNonStringVersion() {
-    $this->moduleHandler->expects($this->atLeastOnce())
-      ->method('moduleExists')
-      ->with('versions')
-      ->will($this->returnValue(TRUE));
-
-    $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen($this->root) + 1);
-    $this->libraryDiscoveryParser->setPaths('module', 'versions', $path);
-
-    $libraries = $this->libraryDiscoveryParser->buildByExtension('versions');
-
-    // As an example, we defined an ISO date in the YAML file and the YAML
-    // parser converts it into a UNIX timestamp.
-    $this->assertNotEquals('2014-12-13', $libraries['invalid-version']['version']);
-    // An example of an ISO date as a string which parses correctly.
-    $this->assertEquals('2014-12-13', $libraries['valid-version']['version']);
-  }
 
   /**
    * Tests that the version property of external libraries is handled.
diff --git a/core/tests/Drupal/Tests/Core/Asset/library_test_files/versions.libraries.yml b/core/tests/Drupal/Tests/Core/Asset/library_test_files/versions.libraries.yml
index bee49f5..7310a09 100644
--- a/core/tests/Drupal/Tests/Core/Asset/library_test_files/versions.libraries.yml
+++ b/core/tests/Drupal/Tests/Core/Asset/library_test_files/versions.libraries.yml
@@ -20,13 +20,3 @@ core-versioned:
       core-versioned.css: {}
   js:
     core-versioned.js: {}
-
-invalid-version:
-  version: 2014-12-13
-  js:
-    versioned.js: {}
-
-valid-version:
-  version: "2014-12-13"
-  js:
-    versioned.js: {}
diff --git a/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php b/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php
index 71948e1..876d3b0 100644
--- a/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/InfoParserUnitTest.php
@@ -152,7 +152,7 @@ public function testInfoParserCommonInfo() {
 description: 'testing info file parsing'
 simple_string: 'A simple string'
 version: "VERSION"
-double_colon: dummyClassName::
+double_colon: dummyClassName::method
 COMMONTEST;
 
     vfsStream::setup('modules');
@@ -164,7 +164,7 @@ public function testInfoParserCommonInfo() {
     $info_values = $this->infoParser->parse(vfsStream::url('modules/fixtures/common_test.info.txt'));
     $this->assertEquals($info_values['simple_string'], 'A simple string', 'Simple string value was parsed correctly.');
     $this->assertEquals($info_values['version'], \Drupal::VERSION, 'Constant value was parsed correctly.');
-    $this->assertEquals($info_values['double_colon'], 'dummyClassName::', 'Value containing double-colon was parsed correctly.');
+    $this->assertEquals($info_values['double_colon'], 'dummyClassName::method', 'Value containing double-colon was parsed correctly.');
   }
 
 }