diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index 5c99f66..bd50660 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -22,11 +22,11 @@ function simpletest_help($route_name, RouteMatchInterface $route_match) {
     case 'help.page.simpletest':
       $output = '';
       $output .= '<h3>' . t('About') . '</h3>';
-      $output .= '<p>' . t('The Testing module provides a framework for running automated tests. It can be used to verify a working state of Drupal before and after any code changes, or as a means for developers to write and execute tests for their modules. For more information, see <a href="!simpletest">the online documentation for the Testing module</a>.', array('!simpletest' => 'https://www.drupal.org/documentation/modules/simpletest')) . '</p>';
+      $output .= '<p>' . t('The Testing module provides a framework for running automated tests. It can be used to verify a working state of Drupal before and after any code changes, or as a means for developers to write and execute tests for their modules. For more information, see <a href="@simpletest">the online documentation for the Testing module</a>.', array('@simpletest' => 'https://www.drupal.org/documentation/modules/simpletest')) . '</p>';
       $output .= '<h3>' . t('Uses') . '</h3>';
       $output .= '<dl>';
       $output .= '<dt>' . t('Running tests') . '</dt>';
-      $output .= '<dd><p>' . t('Visit the <a href="!admin-simpletest">Testing page</a> to display a list of available tests. For comprehensive testing, select <em>all</em> tests, or individually select tests for more targeted testing. Note that it might take several minutes for all tests to complete.', array('!admin-simpletest' => \Drupal::url('simpletest.test_form'))) . '</p>';
+      $output .= '<dd><p>' . t('Visit the <a href="@admin-simpletest">Testing page</a> to display a list of available tests. For comprehensive testing, select <em>all</em> tests, or individually select tests for more targeted testing. Note that it might take several minutes for all tests to complete.', array('@admin-simpletest' => \Drupal::url('simpletest.test_form'))) . '</p>';
       $output .= '<p>' . t('After the tests run, a message will be displayed next to each test group indicating whether tests within it passed, failed, or had exceptions. A pass means that the test returned the expected results, while fail means that it did not. An exception normally indicates an error outside of the test, such as a PHP warning or notice. If there were failures or exceptions, the results will be expanded to show details, and the tests that had failures or exceptions will be indicated in red or pink rows. You can then use these results to refine your code and tests, until all tests pass.') . '</p></dd>';
       $output .= '</dl>';
       return $output;
diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index 1e59712..acc8c81 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -754,9 +754,9 @@ protected function assertNotIdentical($first, $second, $message = '', $group = '
    *   TRUE if the assertion succeeded, FALSE otherwise.
    */
   protected function assertIdenticalObject($object1, $object2, $message = '', $group = 'Other') {
-    $message = $message ?: SafeMarkup::format('!object1 is identical to !object2', array(
-      '!object1' => var_export($object1, TRUE),
-      '!object2' => var_export($object2, TRUE),
+    $message = $message ?: SafeMarkup::format('@object1 is identical to @object2', array(
+      '@object1' => var_export($object1, TRUE),
+      '@object2' => var_export($object2, TRUE),
     ));
     $identical = TRUE;
     foreach ($object1 as $key => $value) {
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 5e86826..cc16100 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -1419,12 +1419,12 @@ protected function curlExec($curl_options, $redirect = FALSE) {
     $this->url = isset($original_url) ? $original_url : curl_getinfo($this->curlHandle, CURLINFO_EFFECTIVE_URL);
 
     $message_vars = array(
-      '!method' => !empty($curl_options[CURLOPT_NOBODY]) ? 'HEAD' : (empty($curl_options[CURLOPT_POSTFIELDS]) ? 'GET' : 'POST'),
+      '@method' => !empty($curl_options[CURLOPT_NOBODY]) ? 'HEAD' : (empty($curl_options[CURLOPT_POSTFIELDS]) ? 'GET' : 'POST'),
       '@url' => isset($original_url) ? $original_url : $url,
       '@status' => $status,
-      '!length' => format_size(strlen($this->getRawContent()))
+      '@length' => format_size(strlen($this->getRawContent()))
     );
-    $message = SafeMarkup::format('!method @url returned @status (!length).', $message_vars);
+    $message = SafeMarkup::format('@method @url returned @status (@length).', $message_vars);
     $this->assertTrue($this->getRawContent() !== FALSE, $message, 'Browser');
     return $this->getRawContent();
   }
@@ -2716,7 +2716,7 @@ protected function assertUrl($path, array $options = array(), $message = '', $gr
   protected function assertResponse($code, $message = '', $group = 'Browser') {
     $curl_code = curl_getinfo($this->curlHandle, CURLINFO_HTTP_CODE);
     $match = is_array($code) ? in_array($curl_code, $code) : $curl_code == $code;
-    return $this->assertTrue($match, $message ? $message : SafeMarkup::format('HTTP response expected !code, actual !curl_code', array('!code' => $code, '!curl_code' => $curl_code)), $group);
+    return $this->assertTrue($match, $message ? $message : SafeMarkup::format('HTTP response expected @code, actual @curl_code', array('@code' => $code, '@curl_code' => $curl_code)), $group);
   }
 
   /**
@@ -2741,7 +2741,7 @@ protected function assertResponse($code, $message = '', $group = 'Browser') {
   protected function assertNoResponse($code, $message = '', $group = 'Browser') {
     $curl_code = curl_getinfo($this->curlHandle, CURLINFO_HTTP_CODE);
     $match = is_array($code) ? in_array($curl_code, $code) : $curl_code == $code;
-    return $this->assertFalse($match, $message ? $message : SafeMarkup::format('HTTP response not expected !code, actual !curl_code', array('!code' => $code, '!curl_code' => $curl_code)), $group);
+    return $this->assertFalse($match, $message ? $message : SafeMarkup::format('HTTP response not expected @code, actual @curl_code', array('@code' => $code, '@curl_code' => $curl_code)), $group);
   }
 
   /**
