diff --git a/core/modules/simpletest/src/AssertContentTrait.php b/core/modules/simpletest/src/AssertContentTrait.php
index 4efee0e..fc5ddbc 100644
--- a/core/modules/simpletest/src/AssertContentTrait.php
+++ b/core/modules/simpletest/src/AssertContentTrait.php
@@ -65,9 +65,8 @@ protected function setRawContent($content) {
     $this->plainTextContent = NULL;
     $this->elements = NULL;
     $this->drupalSettings = array();
-    $result = $this->xpath('//body/script[@type="application/json"][@data-drupal-selector="drupal-settings-json"]');
-    if ($result) {
-      $this->drupalSettings = Json::decode((string) $result[0]);
+    if (preg_match('@<script type="application/json" data-drupal-selector="drupal-settings-json">([^<]*)</script>@', $content, $matches)) {
+      $this->drupalSettings = Json::decode($matches[1]);
     }
   }
 
diff --git a/core/modules/system/src/Tests/Common/AttachedAssetsTest.php b/core/modules/system/src/Tests/Common/AttachedAssetsTest.php
index ca8dbc6..e9a1974 100644
--- a/core/modules/system/src/Tests/Common/AttachedAssetsTest.php
+++ b/core/modules/system/src/Tests/Common/AttachedAssetsTest.php
@@ -185,9 +185,9 @@ function testAggregation() {
     $rendered_footer_js = \Drupal::service('asset.js.collection_renderer')->render($footer_js);
     $this->assertTrue(
       count($rendered_footer_js) == 2
-      && substr($rendered_footer_js[0]['#value'], 0, 20) === 'var drupalSettings ='
+      && $rendered_footer_js[0]['#attributes']['data-drupal-selector'] === 'drupal-settings-json'
       && substr($rendered_footer_js[1]['#attributes']['src'], 0, 7) === 'http://',
-      'There are 2 JavaScript assets in the footer: one with drupalSettings, one with the sole aggregated JavaScript asset.'
+      'There are 2 JavaScript assets in the footer: one with drupal settings, one with the sole aggregated JavaScript asset.'
     );
   }
 
@@ -206,9 +206,9 @@ function testSettings() {
     $rendered_js = $this->renderer->renderPlain($js_render_array);
 
     // Parse the generated drupalSettings <script> back to a PHP representation.
-    $startToken = 'drupalSettings = ';
+    $startToken = '{';
     $endToken = '}';
-    $start = strpos($rendered_js, $startToken) + strlen($startToken);
+    $start = strpos($rendered_js, $startToken);
     $end = strrpos($rendered_js, $endToken);
     $json  = Unicode::substr($rendered_js, $start, $end - $start + 1);
     $parsed_settings = Json::decode($json);