Update to Drupal 8.2.0. For more information, see https://www.drupal.org/project/drupal/releases/8.2.0

core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace Drupal\FunctionalJavascriptTests\Core\Session;
+
+use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
+use Drupal\menu_link_content\Entity\MenuLinkContent;
+
+/**
+ * Tests that sessions don't expire.
+ *
+ * @group session
+ */
+class SessionTest extends JavascriptTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['menu_link_content', 'block'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $account = $this->drupalCreateUser();
+    $this->drupalLogin($account);
+
+    $menu_link_content = MenuLinkContent::create([
+      'title' => 'Link to front page',
+      'menu_name' => 'tools',
+      'link' => ['uri' => 'route:<front>'],
+    ]);
+    $menu_link_content->save();
+
+    $this->drupalPlaceBlock('system_menu_block:tools');
+  }
+
+  /**
+   * Tests that the session doesn't expire.
+   *
+   * Makes sure that drupal_valid_test_ua() works for multiple requests
+   * performed by the Mink browser. The SIMPLETEST_USER_AGENT cookie must always
+   * be valid.
+   */
+  public function testSessionExpiration() {
+    // Visit the front page and click the link back to the front page a large
+    // number of times.
+    $this->drupalGet('<front>');
+
+    $session_assert = $this->assertSession();
+
+    $page = $this->getSession()->getPage();
+
+    for ($i = 0; $i < 25; $i++) {
+      $page->clickLink('Link to front page');
+      $session_assert->statusCodeEquals(200);
+    }
+  }
+
+}