Update to Drupal 8.1.1. For more information, see https://www.drupal.org/node/2718713

core/tests/Drupal/Tests/WebAssert.php

@@ -0,0 +1,67 @@
+<?php
+
+namespace Drupal\Tests;
+
+use Behat\Mink\WebAssert as MinkWebAssert;
+use Behat\Mink\Element\TraversableElement;
+use Behat\Mink\Exception\ElementNotFoundException;
+
+/**
+ * Defines a class with methods for asserting presence of elements during tests.
+ */
+class WebAssert extends MinkWebAssert {
+
+  /**
+   * Checks that specific button exists on the current page.
+   *
+   * @param string $button
+   *   One of id|name|label|value for the button.
+   * @param \Behat\Mink\Element\TraversableElement $container
+   *   (optional) The document to check against. Defaults to the current page.
+   *
+   * @return \Behat\Mink\Element\NodeElement
+   *   The matching element.
+   *
+   * @throws \Behat\Mink\Exception\ElementNotFoundException
+   *   When the element doesn't exist.
+   */
+  public function buttonExists($button, TraversableElement $container = NULL) {
+    $container = $container ?: $this->session->getPage();
+    $node = $container->findButton($button);
+
+    if ($node === NULL) {
+      throw new ElementNotFoundException($this->session, 'button', 'id|name|label|value', $button);
+    }
+
+    return $node;
+  }
+
+  /**
+   * Checks that specific select field exists on the current page.
+   *
+   * @param string $select
+   *   One of id|name|label|value for the select field.
+   * @param \Behat\Mink\Element\TraversableElement $container
+   *   (optional) The document to check against. Defaults to the current page.
+   *
+   * @return \Behat\Mink\Element\NodeElement
+   *   The matching element
+   *
+   * @throws \Behat\Mink\Exception\ElementNotFoundException
+   *   When the element doesn't exist.
+   */
+  public function selectExists($select, TraversableElement $container = NULL) {
+    $container = $container ?: $this->session->getPage();
+    $node = $container->find('named', array(
+      'select',
+      $this->session->getSelectorsHandler()->xpathLiteral($select),
+    ));
+
+    if ($node === NULL) {
+      throw new ElementNotFoundException($this->session, 'select', 'id|name|label|value', $select);
+    }
+
+    return $node;
+  }
+
+}