diff --git a/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php b/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
index e07cb3ce0c..8a9be6354e 100644
--- a/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
+++ b/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
@@ -38,6 +38,41 @@ class TimestampTest extends BrowserTestBase {
    */
   protected $field;
 
+  /**
+   * A field name to use in this test class..
+   *
+   * @var string
+   */
+  protected $field_name;
+
+  /**
+   * A type to use in this test class.
+   *
+   * @var string
+   */
+  protected $type;
+
+  /**
+   * A widget type to use in this test class.
+   *
+   * @var string
+   */
+  protected $widget_type;
+
+  /**
+   * A formatter type to use in this test class.
+   *
+   * @var string
+   */
+  protected $formatter_type;
+
+  /**
+   * A formDisplayOptions to use in this test class.
+   *
+   * @var array
+   */
+  protected $formDisplayOptions;
+
   /**
    * {@inheritdoc}
    */
@@ -206,4 +241,4 @@ public function testWidget() {
     $this->assertSession()->fieldValueEquals('field_timestamp[0][value][time]', $date->format($time_format));
   }
 
-}
+}