diff --git a/core/modules/file/lib/Drupal/file/Plugin/views/field/Extension.php b/core/modules/file/lib/Drupal/file/Plugin/views/field/Extension.php
index 9822cce..1663f04 100644
--- a/core/modules/file/lib/Drupal/file/Plugin/views/field/Extension.php
+++ b/core/modules/file/lib/Drupal/file/Plugin/views/field/Extension.php
@@ -3,6 +3,7 @@
 /**
  * @file
  * Definition of views_handler_field_file_extension.
+ * @todo Test!
  */
 
 namespace Drupal\file\Plugin\views\field;
@@ -19,43 +20,43 @@
  */
 class Extension extends FieldPluginBase {
 
+  /**
+   * {@inheritdoc}
+   */
   protected function defineOptions() {
     $options = parent::defineOptions();
-    $options['fileextension_detect_tar'] = array('default' => FALSE, 'bool' => TRUE);
+    $options['extension_detect_tar'] = array('default' => FALSE, 'bool' => TRUE);
     return $options;
   }
 
   /**
-   * Default options form that provides the label widget that all fields
-   * should have.
+   * {@inheritdoc}
    */
   public function buildOptionsForm(&$form, &$form_state) {
     parent::buildOptionsForm($form, $form_state);
-    $form['fileextension_detect_tar'] = array(
+    $form['extension_detect_tar'] = array(
       '#type' => 'checkbox',
       '#title' => t('Detect if tar is part of the extension'),
-      '#description' => t('Detect multiple tar extensions like tar.gz'),
+      '#description' => t("See if the previous extension is '.tar' and if so, add that, so we see 'tar.gz' or 'tar.bz2' instead of just 'gz'."),
       '#default_value' => $this->options['fileextension_max_extension_parts'],
     );
   }
 
   function render($values) {
-    if (!$this->options['fileextension_detect_tar']) {
-      $value = $this->get_value($values);
+    $value = $this->get_value($values);
+    if (!$this->options['extension_detect_tar']) {
       if (preg_match('/\.([^\.]+)$/', $value, $match)) {
         return $this->sanitizeValue($match[1]);
       }
     }
     else {
-      $file_parts = explode('.', basename($this->get_value($values)));
+      $file_parts = explode('.', basename($value));
       // If there is an extension.
       if (count($file_parts) > 1) {
         $extension = array_pop($file_parts);
-        // See if the previous extension is '.tar' and if so, add that, so we
-        // see 'tar.gz' or 'tar.bz2' instead of just 'gz'.
         $last_part_in_name = array_pop($file_parts);
         if ($last_part_in_name === 'tar') {
-          $extension = $last_part_in_name . '.' . $extension;
+          $extension = 'tar.' . $extension;
         }
         return $this->sanitizeValue($extension);
       }
diff --git a/core/modules/file/lib/Drupal/file/Tests/ExtensionViewsFieldTest.php b/core/modules/file/lib/Drupal/file/Tests/ExtensionViewsFieldTest.php
new file mode 100644
index 0000000..c2bd69c
--- /dev/null
+++ b/core/modules/file/lib/Drupal/file/Tests/ExtensionViewsFieldTest.php
@@ -0,0 +1,80 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\file\Tests\ExtensionViewsFieldTest.php
+ */
+
+namespace Drupal\file\Tests;
+
+use Drupal\views\Tests\ViewUnitTestBase;
+
+/**
+ * Tests the core Drupal\file\Plugin\views\field\Extension handler.
+ *
+ * @see CommonXssUnitTest
+ */
+class ExtensionViewsFieldTest extends ViewUnitTestBase {
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = array('test_view');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Field: File extension',
+      'description' => 'Test the core Drupal\file\Plugin\views\field\Extension handler.',
+      'group' => 'Views Handlers',
+    );
+  }
+
+  function dataSet() {
+    $data = parent::dataSet();
+    $data[0]['name'] = 'file.png';
+    $data[1]['name'] = 'file.tar';
+    $data[2]['name'] = 'file.tar.gz';
+    $data[3]['name'] = 'file';
+
+    return $data;
+  }
+
+  function viewsData() {
+    $data = parent::viewsData();
+    $data['views_test_data']['name']['field']['id'] = 'file_extension';
+    $data['views_test_data']['name']['real field'] = 'name';
+
+    return $data;
+  }
+
+  public function testFieldExtension() {
+    $view = views_get_view('test_view');
+    $view->setDisplay();
+
+    $view->displayHandlers->get('default')->overrideOption('fields', array(
+      'name' => array(
+        'id' => 'extension',
+        'table' => 'views_test_data',
+        'field' => 'name',
+        //'plugin_id' => 'file_extension',
+      ),
+    ));
+
+    $this->executeView($view);
+
+    // Test without the tar option.
+    $this->assertEqual($view->field['name']->advanced_render($view->result[0]), 'png');
+    $this->assertEqual($view->field['name']->advanced_render($view->result[1]), 'tar');
+    $this->assertEqual($view->field['name']->advanced_render($view->result[2]), 'gz');
+    $this->assertEqual($view->field['name']->advanced_render($view->result[3]), '');
+    // Test with the tar option.
+    $view->field['name']->options['extension_detect_tar'] = TRUE;
+    $this->assertEqual($view->field['name']->advanced_render($view->result[0]), 'png');
+    $this->assertEqual($view->field['name']->advanced_render($view->result[1]), 'tar');
+    $this->assertEqual($view->field['name']->advanced_render($view->result[2]), 'tar.gz');
+    $this->assertEqual($view->field['name']->advanced_render($view->result[3]), '');
+  }
+
+}