diff -u b/core/modules/simpletest/src/Form/SimpletestResultsForm.php b/core/modules/simpletest/src/Form/SimpletestResultsForm.php
--- b/core/modules/simpletest/src/Form/SimpletestResultsForm.php
+++ b/core/modules/simpletest/src/Form/SimpletestResultsForm.php
@@ -61,28 +61,28 @@
     // Initialize image mapping property.
     $image_pass = array(
       '#theme' => 'image',
-      '#uri' => 'core/misc/icons/73b355/check.png',
+      '#uri' => 'core/misc/icons/73b355/check.svg',
       '#width' => 18,
       '#height' => 18,
       '#alt' => $this->t('Pass'),
     );
     $image_fail = array(
       '#theme' => 'image',
-      '#uri' => 'core/misc/icons/ea2800/error.png',
+      '#uri' => 'core/misc/icons/ea2800/error.svg',
       '#width' => 18,
       '#height' => 18,
       '#alt' => $this->t('Fail'),
     );
     $image_exception = array(
       '#theme' => 'image',
-      '#uri' => 'core/misc/icons/e29700/warning.png',
+      '#uri' => 'core/misc/icons/e29700/warning.svg',
       '#width' => 18,
       '#height' => 18,
       '#alt' => $this->t('Exception'),
     );
     $image_debug = array(
       '#theme' => 'image',
-      '#uri' => 'core/misc/icons/e29700/warning.png',
+      '#uri' => 'core/misc/icons/e29700/warning.svg',
       '#width' => 18,
       '#height' => 18,
       '#alt' => $this->t('Debug'),
diff -u b/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
--- b/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -743,7 +743,7 @@
 
     $message = '<hr />ID #' . $this->verboseId . ' (<a href="' . $this->verboseClassName . '-' . ($this->verboseId - 1) . '-' . $this->testId . '.html">Previous</a> | <a href="' . $this->verboseClassName . '-' . ($this->verboseId + 1) . '-' . $this->testId . '.html">Next</a>)<hr />' . $message;
     $verbose_filename =  $this->verboseClassName . '-' . $this->verboseId . '-' . $this->testId . '.html';
-    if (file_put_contents($this->verboseDirectory . '/' . $verbose_filename, $message, FILE_APPEND)) {
+    if (file_put_contents($this->verboseDirectory . '/' . $verbose_filename, $message)) {
       $url = $this->verboseDirectoryUrl . '/' . $verbose_filename;
       // Not using l() to avoid invoking the theme system, so that unit tests
       // can use verbose() as well.
diff -u b/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
--- b/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -6,9 +6,13 @@
  */
 
 use Drupal\Component\Utility\Timer;
+use Drupal\Component\Uuid\Php;
 use Drupal\Core\Database\Database;
+use Drupal\Core\Form\FormState;
 use Drupal\Core\Site\Settings;
+use Drupal\Core\StreamWrapper\PublicStream;
 use Drupal\Core\Test\TestRunnerKernel;
+use Drupal\simpletest\Form\SimpletestResultsForm;
 use Symfony\Component\HttpFoundation\Request;
 
 $autoloader = require_once __DIR__ . '/../vendor/autoload.php';
@@ -1079,24 +1083,37 @@
  */
 function simpletest_script_open_browser() {
-  global $args, $test_ids;
+  global $test_ids;
 
+  // Generate html results.
+  $connection = Database::getConnection('default', 'test-runner');
+  $form = new SimpletestResultsForm($connection);
+  $form_array = $form->buildForm(array(), new FormState(), implode('+', $test_ids));
+  unset($form_array['action']);
+  unset($form_array['#action']);
+  $html = drupal_render($form_array);
+  // Unfortunately calling this tries to write config!
+  //$html = drupal_get_css() . $html;
+  $html = '<head><link type="text/css" rel="stylesheet" href="'. file_create_url(drupal_get_path('module', 'simpletest') . '/css/simpletest.module.css') . '" media="all"></head><body>' .$html .'</body>';
+  $uuid = new Php();
+  $filename = PublicStream::basePath() . '/simpletest/verbose/results-'. $uuid->generate() .'.html';
+  file_put_contents($filename, $html);
   // See if we can find an OS helper to open URLs in default browser.
   if (shell_exec('which xdg-open')) {
     $browser = 'xdg-open';
   }
-  else if (shell_exec('which open')) {
+  elseif (shell_exec('which open')) {
     $browser = 'open';
   }
-  else if (substr(PHP_OS, 0, 3) == 'WIN') {
+  elseif (substr(PHP_OS, 0, 3) == 'WIN') {
     $browser = 'start';
   }
   else {
     // Can't find a valid browser.
+    // @todo Output some help giving the user the filename of the html to open.
     $browser = FALSE;
   }
 
   if ($browser) {
-    $url = $args['url'] . '/admin/config/development/testing/results/' . urlencode(implode('+', $test_ids));
-    shell_exec($browser . ' ' . escapeshellarg($url));
+    shell_exec($browser . ' ' . escapeshellarg($filename));
   }
 }