reverted:
--- b/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php
+++ a/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php
@@ -366,60 +366,4 @@
     return $this->session->evaluateScript($full_javascript_visibility_test);
   }
 
-  /**
-   * The use of statusCodeEquals() is not available.
-   *
-   * @param int $code
-   *   The status code.
-   *
-   * @throws \Behat\Mink\Exception\UnsupportedDriverActionException
-   *   Throws an exception on use.
-   */
-  public function statusCodeEquals($code) {
-    throw new UnsupportedDriverActionException('The use of statusCodeEquals() is not available in a functional JavaScript test.', $this->session->getDriver());
-  }
-
-  /**
-   * The use of statusCodeNotEquals() is not available.
-   *
-   * @param int $code
-   *   The status code.
-   *
-   * @throws \Behat\Mink\Exception\UnsupportedDriverActionException
-   *   Throws an exception on use.
-   */
-  public function statusCodeNotEquals($code) {
-    throw new UnsupportedDriverActionException('The use of statusCodeNotEquals() is not available in a functional JavaScript test.', $this->session->getDriver());
-  }
-
-  /**
-   * The use of responseHeaderEquals() is not available.
-   *
-   * @param string $name
-   *   The name of the header.
-   * @param string $value
-   *   The value to check the header against.
-   *
-   * @throws \Behat\Mink\Exception\UnsupportedDriverActionException
-   *   Throws an exception on use.
-   */
-  public function responseHeaderEquals($name, $value) {
-    throw new UnsupportedDriverActionException('The use of responseHeaderEquals() is not available in a functional JavaScript test.', $this->session->getDriver());
-  }
-
-  /**
-   * The use of responseHeaderNotEquals() is not available.
-   *
-   * @param string $name
-   *   The name of the header.
-   * @param string $value
-   *   The value to check the header against.
-   *
-   * @throws \Behat\Mink\Exception\UnsupportedDriverActionException
-   *   Throws an exception on use.
-   */
-  public function responseHeaderNotEquals($name, $value) {
-    throw new UnsupportedDriverActionException('The use of responseHeaderNotEquals() is not available in a functional JavaScript test.', $this->session->getDriver());
-  }
-
 }