Update to Drupal 8.1.5. For more information, see https://www.drupal.org/project/drupal/releases/8.1.5

core/modules/simpletest/tests/src/Functional/BrowserTestBaseTest.php

@@ -33,6 +33,9 @@ class BrowserTestBaseTest extends BrowserTestBase {
     // Test page contains some text.
     $this->assertSession()->pageTextContains('Test page text.');
 
+    // Response includes cache tags that we can assert.
+    $this->assertSession()->responseHeaderEquals('X-Drupal-Cache-Tags', 'rendered');
+
     // Test drupalGet with a url object.
     $url = Url::fromRoute('test_page_test.render_title');
     $this->drupalGet($url);

core/modules/simpletest/tests/src/Unit/TestBaseTest.php

@@ -5,6 +5,7 @@ namespace Drupal\Tests\simpletest\Unit;
 use Drupal\Tests\UnitTestCase;
 
 /**
+ * @requires extension curl
  * @coversDefaultClass \Drupal\simpletest\TestBase
  * @group simpletest
  */

core/modules/simpletest/tests/src/Unit/WebTestBaseTest.php

@@ -5,6 +5,7 @@ namespace Drupal\Tests\simpletest\Unit;
 use Drupal\Tests\UnitTestCase;
 
 /**
+ * @requires extension curl
  * @coversDefaultClass \Drupal\simpletest\WebTestBase
  * @group simpletest
  */