diff --git a/modules/file/tests/file.test b/modules/file/tests/file.test
index 1510a69..41e97cd 100644
--- a/modules/file/tests/file.test
+++ b/modules/file/tests/file.test
@@ -597,6 +597,56 @@ class FileFieldWidgetTestCase extends FileFieldTestCase {
   }
 
   /**
+   * Tests validation with the Upload button.
+   */
+  function testWidgetValidation() {
+    $type_name = 'article';
+    $field_name = strtolower($this->randomName());
+    $this->createFileField($field_name, $type_name);
+    $this->updateFileField($field_name, $type_name, array('file_extensions' => 'txt'));
+
+    foreach (array('nojs', 'js') as $type) {
+      // Create node and prepare files for upload.
+      $node = $this->drupalCreateNode(array('type' => 'article'));
+      $nid = $node->nid;
+      $this->drupalGet("node/$nid/edit");
+      $test_file_text = $this->getTestFile('text');
+      $test_file_image = $this->getTestFile('image');
+      $field = field_info_field($field_name);
+      $name = 'files[' . $field_name . '_' . LANGUAGE_NONE . '_0]';
+
+      // Upload file with incorrect extension, check for validation error.
+      $edit[$name] = drupal_realpath($test_file_image->uri);
+      switch ($type) {
+        case 'nojs':
+          $this->drupalPost(NULL, $edit, t('Upload'));
+          break;
+
+        case 'js':
+          $button = $this->xpath('//input[@type="submit" and @value="' . t('Upload') . '"]');
+          $this->drupalPostAJAX(NULL, $edit, array((string) $button[0]['name'] => (string) $button[0]['value']));
+          break;
+      }
+      $error_message = t('Only files with the following extensions are allowed: %files-allowed.', array('%files-allowed' => 'txt'));
+      $this->assertRaw($error_message, t('Validation error when file with wrong extension uploaded (JSMode=%type).', array('%type' => $type)));
+
+      // Upload file with correct extension, check that error message is removed.
+      $edit[$name] = drupal_realpath($test_file_text->uri);
+      switch ($type) {
+        case 'nojs':
+          $this->drupalPost(NULL, $edit, t('Upload'));
+          break;
+
+        case 'js':
+          $button = $this->xpath('//input[@type="submit" and @value="' . t('Upload') . '"]');
+          $this->drupalPostAJAX(NULL, $edit, array((string) $button[0]['name'] => (string) $button[0]['value']));
+          break;
+      }
+      $this->assertNoRaw($error_message, t('Validation error removed when file with correct extension uploaded (JSMode=%type).', array('%type' => $type)));
+    }
+  }
+
+  /**
    * Helper for testing exploiting the temporary file removal using fid.
    *
    * @param int $victim_uid