diff --git a/core/modules/simpletest/src/AssertContentTrait.php b/core/modules/simpletest/src/AssertContentTrait.php
index 9eda1c5..73af1eb 100644
--- a/core/modules/simpletest/src/AssertContentTrait.php
+++ b/core/modules/simpletest/src/AssertContentTrait.php
@@ -311,8 +311,9 @@ protected function assertLink($label, $index = 0, $message = '', $group = 'Other
    *   Text between the anchor tags.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -337,8 +338,9 @@ protected function assertNoLink($label, $message = '', $group = 'Other') {
    *   Link position counting from zero.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -361,8 +363,9 @@ protected function assertLinkByHref($href, $index = 0, $message = '', $group = '
    *   The full or partial value of the 'href' attribute of the anchor tag.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -385,8 +388,9 @@ protected function assertNoLinkByHref($href, $message = '', $group = 'Other') {
    *   The full or partial value of the 'href' attribute of the anchor tag.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -411,8 +415,9 @@ protected function assertNoLinkByHrefInMainRegion($href, $message = '', $group =
    *   Raw (HTML) string to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -438,8 +443,9 @@ protected function assertRaw($raw, $message = '', $group = 'Other') {
    *   Raw (HTML) string to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -465,8 +471,9 @@ protected function assertNoRaw($raw, $message = '', $group = 'Other') {
    *   Raw (HTML) string to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -493,8 +500,9 @@ protected function assertEscaped($raw, $message = '', $group = 'Other') {
    *   Raw (HTML) string to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -521,8 +529,9 @@ protected function assertNoEscaped($raw, $message = '', $group = 'Other') {
    *   Plain text to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -548,8 +557,9 @@ protected function assertText($text, $message = '', $group = 'Other') {
    *   Plain text to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -574,8 +584,9 @@ protected function assertNoText($text, $message = '', $group = 'Other') {
    *   Plain text to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -606,8 +617,9 @@ protected function assertTextHelper($text, $message = '', $group = 'Other', $not
    *   Plain text to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -632,8 +644,9 @@ protected function assertUniqueText($text, $message = '', $group = 'Other') {
    *   Plain text to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -656,8 +669,9 @@ protected function assertNoUniqueText($text, $message = '', $group = 'Other') {
    *   Plain text to look for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -690,8 +704,9 @@ protected function assertUniqueTextHelper($text, $message = '', $group = 'Other'
    *   Perl regex to look for including the regex delimiters.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -715,8 +730,9 @@ protected function assertPattern($pattern, $message = '', $group = 'Other') {
    *   Perl regex to look for including the regex delimiters.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -763,8 +779,9 @@ protected function assertTextPattern($pattern, $message = NULL, $group = 'Other'
    *   The string the title should be.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -792,8 +809,9 @@ protected function assertTitle($title, $message = '', $group = 'Other') {
    *   The string the title should not be.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -825,8 +843,9 @@ protected function assertNoTitle($title, $message = '', $group = 'Other') {
    *   The expected themed output string.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -868,8 +887,9 @@ protected function assertThemeOutput($callback, array $variables = array(), $exp
    *   checking the actual value, while still checking that the field exists.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -925,8 +945,9 @@ protected function assertFieldsByValue($fields, $value = NULL, $message = '', $g
    *   exists.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -975,8 +996,9 @@ protected function getSelectedItem(\SimpleXMLElement $element) {
    *   page does not match it.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1015,8 +1037,9 @@ protected function assertNoFieldByXPath($xpath, $value = NULL, $message = '', $g
    *   exists.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1055,8 +1078,9 @@ protected function assertFieldByName($name, $value = NULL, $message = NULL, $gro
    *   default value ('') asserts that the field value is not an empty string.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1082,8 +1106,9 @@ protected function assertNoFieldByName($name, $value = '', $message = '', $group
    *   string.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1109,8 +1134,9 @@ protected function assertFieldById($id, $value = '', $message = '', $group = 'Br
    *   value ('') asserts that the field value is not an empty string.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1131,8 +1157,9 @@ protected function assertNoFieldById($id, $value = '', $message = '', $group = '
    *   ID of field to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1154,8 +1181,9 @@ protected function assertFieldChecked($id, $message = '', $group = 'Browser') {
    *   ID of field to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1179,8 +1207,9 @@ protected function assertNoFieldChecked($id, $message = '', $group = 'Browser')
    *   Option to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1204,8 +1233,9 @@ protected function assertOption($id, $option, $message = '', $group = 'Browser')
    *   Option to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1229,8 +1259,9 @@ protected function assertOptionWithDrupalSelector($drupal_selector, $option, $me
    *   Option to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1255,8 +1286,9 @@ protected function assertNoOption($id, $option, $message = '', $group = 'Browser
    *   Option to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1282,8 +1314,9 @@ protected function assertOptionSelected($id, $option, $message = '', $group = 'B
    *   Option to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1309,8 +1342,9 @@ protected function assertOptionSelectedWithDrupalSelector($drupal_selector, $opt
    *   Option to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1332,8 +1366,9 @@ protected function assertNoOptionSelected($id, $option, $message = '', $group =
    *   Name or ID of field to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1354,8 +1389,9 @@ protected function assertField($field, $message = '', $group = 'Other') {
    *   Name or ID of field to assert.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -1374,8 +1410,9 @@ protected function assertNoField($field, $message = '', $group = 'Other') {
    *
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index cfccbcf..5b03712 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -2630,8 +2630,9 @@ protected function drupalGetMails($filter = array()) {
    *   (optional) Any additional options to pass for $path to the url generator.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -2670,8 +2671,9 @@ protected function assertUrl($path, array $options = array(), $message = '', $gr
    *   of all codes see http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -2695,8 +2697,9 @@ protected function assertResponse($code, $message = '', $group = 'Browser') {
    *   of all codes see http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -2724,8 +2727,9 @@ protected function assertNoResponse($code, $message = '', $group = 'Browser') {
    *   Value of the field to assert.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -2752,8 +2756,9 @@ protected function assertMail($name, $value = '', $message = '', $group = 'Email
    *   Number of emails to search for string, starting with most recent.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -2792,8 +2797,9 @@ protected function assertMailString($field_name, $string, $email_depth, $message
    *   Pattern to search for.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
diff --git a/core/modules/views/src/Tests/Handler/FieldKernelTest.php b/core/modules/views/src/Tests/Handler/FieldKernelTest.php
index b1897cd..70940d0 100644
--- a/core/modules/views/src/Tests/Handler/FieldKernelTest.php
+++ b/core/modules/views/src/Tests/Handler/FieldKernelTest.php
@@ -105,8 +105,9 @@ public function testQuery() {
    *   The value to search for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not
@@ -129,8 +130,9 @@ protected function assertSubString($haystack, $needle, $message = '', $group = '
    *   The value to search for.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use format_string() to embed variables in the message text, not
-   *   t(). If left blank, a default message will be displayed.
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
    * @param string $group
    *   (optional) The group this message is in, which is displayed in a column
    *   in test output. Use 'Debug' to indicate this is debugging output. Do not