diff --git a/core/modules/language/src/ConfigurableLanguageInterface.php b/core/modules/language/src/ConfigurableLanguageInterface.php
index 03cd14d..16536a1 100644
--- a/core/modules/language/src/ConfigurableLanguageInterface.php
+++ b/core/modules/language/src/ConfigurableLanguageInterface.php
@@ -8,10 +8,11 @@
 namespace Drupal\language;
 
 use Drupal\Core\Config\Entity\ConfigEntityInterface;
+use Drupal\Core\Language\LanguageInterface;
 
 /**
  * Provides an interface defining a language entity.
  */
-interface ConfigurableLanguageInterface extends ConfigEntityInterface {
+interface ConfigurableLanguageInterface extends ConfigEntityInterface, LanguageInterface {
 
 }
diff --git a/core/modules/language/src/Entity/ConfigurableLanguage.php b/core/modules/language/src/Entity/ConfigurableLanguage.php
index c252010..eda4d9a 100644
--- a/core/modules/language/src/Entity/ConfigurableLanguage.php
+++ b/core/modules/language/src/Entity/ConfigurableLanguage.php
@@ -109,9 +109,20 @@ class ConfigurableLanguage extends ConfigEntityBase implements ConfigurableLangu
   protected $preSaveMultilingual;
 
   /**
+   * The language negotiation method used when a language was detected.
+   *
+   * The method ID, for example
+   * \Drupal\language\LanguageNegotiatorInterface::METHOD_ID.
+   *
+   * @var string
+   */
+  public $methodId;
+
+  /**
    * Sets the default flag on the language entity.
    *
    * @param bool $default
+   *   TRUE if the language entity is the site default language, FALSE if not.
    */
   public function setDefault($default) {
     $this->default = $default;
@@ -201,7 +212,9 @@ protected function toLanguageObject() {
   /**
    * {@inheritdoc}
    *
-   * @throws \RuntimeException
+   * @throws \DeleteDefaultLanguageException
+   *   Exception thrown if we're trying to delete the default language entity.
+   *   This is not allowed as a site must have a default language.
    */
   public static function preDelete(EntityStorageInterface $storage, array $entities) {
     $default_langcode = static::getDefaultLangcode();
@@ -235,4 +248,75 @@ protected static function getDefaultLangcode() {
     return $language->getId();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getName() {
+    return $this->label();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setName($name) {
+    $this->label = $name;
+
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getId() {
+    return $this->id();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDirection() {
+    return $this->direction;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setDirection($direction) {
+    $this->direction = $direction;
+
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getWeight() {
+    return $this->weight;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setWeight($weight) {
+    $this->weight = $weight;
+
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getNegotiationMethodId() {
+    return $this->methodId;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setNegotiationMethodId($method_id) {
+    $this->methodId = $method_id;
+
+    return $this;
+  }
+
 }
diff --git a/core/modules/language/src/Tests/ConfigurableLanguageUnitTest.php b/core/modules/language/src/Tests/ConfigurableLanguageUnitTest.php
new file mode 100644
index 0000000..7f193d4
--- /dev/null
+++ b/core/modules/language/src/Tests/ConfigurableLanguageUnitTest.php
@@ -0,0 +1,80 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\language\Tests\ConfigurableLanguageUnitTest.
+ */
+
+namespace Drupal\language\Tests;
+
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests the ConfigurableLanguage entity class.
+ *
+ * @group language
+ * @coversDefaultClass \Drupal\language\Entity\ConfigurableLanguage
+ * @see \Drupal\language\Entity\ConfigurableLanguage.
+ */
+class ConfigurableLanguageUnitTest extends UnitTestCase {
+
+  /**
+   * The Entity under test.
+   *
+   * @var \Drupal\language\Entity\ConfigurableLanguage;
+   */
+  protected $configurableLanguage;
+
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->configurableLanguage = new ConfigurableLanguage(array(), 'configurable_language');
+  }
+
+  /**
+   * @covers ::setDirection
+   * @covers ::getDirection
+   */
+  public function testDirection() {
+    // Direction of language writing, an integer. Usually either
+    // ConfigurableLanguage::DIRECTION_LTR or
+    // ConfigurableLanguage::DIRECTION_RTL.
+    $set_direction_ltr = ConfigurableLanguage::DIRECTION_LTR;
+    $this->configurableLanguage->setDirection($set_direction_ltr);
+    $this->assertEquals($this->configurableLanguage->getDirection(), $set_direction_ltr, 'LTR direction written and read correctly.');
+
+    // Test direction again, setting direction to RTL.
+    $set_direction_rtl = ConfigurableLanguage::DIRECTION_RTL;
+    $this->configurableLanguage->setDirection($set_direction_rtl);
+    $this->assertEquals($this->configurableLanguage->getDirection(), $set_direction_rtl, 'RTL direction written and read correctly.');
+  }
+
+  /**
+   * @covers ::setWeight
+   * @covers ::getWeight
+   */
+  public function testWeight() {
+    // The weight, an integer. Used to order languages with larger positive
+    // weights sinking items toward the bottom of lists.
+    $set_weight = -5;
+    $this->configurableLanguage->setWeight($set_weight);
+    $this->assertEquals($this->configurableLanguage->getWeight(), $set_weight, 'Weight written and read correctly.');
+  }
+
+  /**
+   * @covers::setNegotiationMethodId
+   * @covers::setNegotiationMethodId
+   */
+  public function testNegotiationMethodId(){
+    // Language's negotiation method ID, a string. E.g.
+    // \Drupal\language\LanguageNegotiatorInterface::METHOD_ID.
+    $set_method_id = 'language-foomethod';
+    $this->configurableLanguage->setNegotiationMethodId($set_method_id);
+    $this->assertEquals($this->configurableLanguage->getNegotiationMethodId(), $set_method_id, 'Negotiation Method Identifier written and read correctly.');
+  }
+
+}