diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 03572a6ccf4b72c2d0cf43aff02d2d4661155835..bedf474e4bbc891ee6cf33150a73533beaa96f15 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -344,7 +344,7 @@ function t($string, array $args = array(), array $options = array()) {
  * @see t()
  * @ingroup sanitization
  */
-function format_string($string, array $args = array()) {
+function format_string($string, array $args) {
   return SafeMarkup::format($string, $args);
 }
 
diff --git a/core/lib/Drupal/Component/Utility/SafeMarkup.php b/core/lib/Drupal/Component/Utility/SafeMarkup.php
index 91a2f1e31088e128a6ea5341565ea77af3cb5913..ee25f86725f9012dcaa9e38443eac4bbbeaed1bf 100644
--- a/core/lib/Drupal/Component/Utility/SafeMarkup.php
+++ b/core/lib/Drupal/Component/Utility/SafeMarkup.php
@@ -218,7 +218,7 @@ public static function checkPlain($text) {
    *
    * @see t()
    */
-  public static function format($string, array $args = array()) {
+  public static function format($string, array $args) {
     $safe = TRUE;
 
     // Transform arguments before inserting them.
diff --git a/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityAdapter.php b/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityAdapter.php
index 054d101ba4db2e9118fb3ea42f71846fc583d1fb..5dc1d2c98c3498b64fc7f575f3de62bfd24f12c4 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityAdapter.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityAdapter.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\Core\Entity\Plugin\DataType;
 
-use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Entity\FieldableEntityInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\TypedData\EntityDataDefinition;
@@ -114,7 +113,7 @@ public function set($property_name, $value, $notify = TRUE) {
    */
   public function getProperties($include_computed = FALSE) {
     if (!isset($this->entity)) {
-      throw new MissingDataException(SafeMarkup::format('Unable to get properties as no entity has been provided.'));
+      throw new MissingDataException('Unable to get properties as no entity has been provided.');
     }
     if (!$this->entity instanceof FieldableEntityInterface) {
       // @todo: Add support for config entities in
diff --git a/core/modules/config/src/Tests/ConfigFileContentTest.php b/core/modules/config/src/Tests/ConfigFileContentTest.php
index 1347db588a968a3ea8af1e8640ddd21b6ee8e917..8818f4186108c4acd56459ed99a1ed5eef567a87 100644
--- a/core/modules/config/src/Tests/ConfigFileContentTest.php
+++ b/core/modules/config/src/Tests/ConfigFileContentTest.php
@@ -121,16 +121,16 @@ function testReadWriteConfig() {
     $this->assertNull($config->get('i.dont.exist'), 'Non-existent nested value returned NULL.');
 
     // Read false value.
-    $this->assertEqual($config->get($false_key), '0', format_string("Boolean FALSE value returned the string '0'."));
+    $this->assertEqual($config->get($false_key), '0', "Boolean FALSE value returned the string '0'.");
 
     // Read true value.
-    $this->assertEqual($config->get($true_key), '1', format_string("Boolean TRUE value returned the string '1'."));
+    $this->assertEqual($config->get($true_key), '1', "Boolean TRUE value returned the string '1'.");
 
     // Read null value.
     $this->assertIdentical($config->get('null'), NULL);
 
     // Read false that had been nested in an array value.
-    $this->assertEqual($config->get($casting_array_false_value_key), '0', format_string("Nested boolean FALSE value returned the string '0'."));
+    $this->assertEqual($config->get($casting_array_false_value_key), '0', "Nested boolean FALSE value returned the string '0'.");
 
     // Unset a top level value.
     $config->clear($key);
diff --git a/core/modules/field/src/Tests/String/RawStringFormatterTest.php b/core/modules/field/src/Tests/String/RawStringFormatterTest.php
index 020a2e386e5ba19a4a76bc32b5a5395b2e3d8d88..82f69731f639456cf695f3ddf5484e30b7220243 100644
--- a/core/modules/field/src/Tests/String/RawStringFormatterTest.php
+++ b/core/modules/field/src/Tests/String/RawStringFormatterTest.php
@@ -123,7 +123,7 @@ public function testStringFormatter() {
 
     // Verify the cache tags.
     $build = $entity->{$this->fieldName}->view();
-    $this->assertTrue(!isset($build[0]['#cache']), format_string('The string formatter has no cache tags.'));
+    $this->assertTrue(!isset($build[0]['#cache']), 'The string formatter has no cache tags.');
   }
 
 }
diff --git a/core/modules/field/src/Tests/String/StringFormatterTest.php b/core/modules/field/src/Tests/String/StringFormatterTest.php
index 4af818eb6e161800617a7e3d174b851905c0243e..dcb515e84db86d2fdf5b7c4118ce45e3364837b7 100644
--- a/core/modules/field/src/Tests/String/StringFormatterTest.php
+++ b/core/modules/field/src/Tests/String/StringFormatterTest.php
@@ -123,7 +123,7 @@ public function testStringFormatter() {
 
     // Verify the cache tags.
     $build = $entity->{$this->fieldName}->view();
-    $this->assertTrue(!isset($build[0]['#cache']), format_string('The string formatter has no cache tags.'));
+    $this->assertTrue(!isset($build[0]['#cache']), 'The string formatter has no cache tags.');
 
     $value = $this->randomMachineName();
     $entity->{$this->fieldName}->value = $value;
diff --git a/core/modules/system/src/Tests/Ajax/FrameworkTest.php b/core/modules/system/src/Tests/Ajax/FrameworkTest.php
index c7ccd8b0bdde7c06aaaee93e689b38748591650f..6ab1c5e84b9cdd18e3354acf5a958f31135afeea 100644
--- a/core/modules/system/src/Tests/Ajax/FrameworkTest.php
+++ b/core/modules/system/src/Tests/Ajax/FrameworkTest.php
@@ -165,7 +165,7 @@ public function testLazyLoad() {
     // the first AJAX command.
     $this->assertIdentical($new_settings[$expected['setting_name']], $expected['setting_value'], format_string('Page now has the %setting.', array('%setting' => $expected['setting_name'])));
     $expected_command = new SettingsCommand(array($expected['setting_name'] => $expected['setting_value']), TRUE);
-    $this->assertCommand(array_slice($commands, 0, 1), $expected_command->render(), format_string('The settings command was first.'));
+    $this->assertCommand(array_slice($commands, 0, 1), $expected_command->render(), 'The settings command was first.');
 
     // Verify the expected CSS file was added, both to drupalSettings, and as
     // the second AJAX command for inclusion into the HTML.
diff --git a/core/modules/system/src/Tests/Entity/EntityQueryTest.php b/core/modules/system/src/Tests/Entity/EntityQueryTest.php
index fd4165bb771e3b7c7d888d83369080bc0b153cef..4130804ca1c5fb020022a60c564dc39de177974a 100644
--- a/core/modules/system/src/Tests/Entity/EntityQueryTest.php
+++ b/core/modules/system/src/Tests/Entity/EntityQueryTest.php
@@ -554,7 +554,7 @@ protected function assertBundleOrder($order) {
           }
         }
       }
-      $this->assertTrue($ok, format_string("$i is after all entities in bundle2"));
+      $this->assertTrue($ok, "$i is after all entities in bundle2");
     }
   }
 
diff --git a/core/modules/system/src/Tests/Path/AliasTest.php b/core/modules/system/src/Tests/Path/AliasTest.php
index 4281905144512f1e7e70d744176b1306e4880a97..2ceb4c973f5cb55b475ebf260fb490d33b2dea31 100644
--- a/core/modules/system/src/Tests/Path/AliasTest.php
+++ b/core/modules/system/src/Tests/Path/AliasTest.php
@@ -52,7 +52,7 @@ function testCRUD() {
 
     // Load alias by source path.
     $loadedAlias = $aliasStorage->load(array('source' => '/node/1'));
-    $this->assertEqual($loadedAlias['alias'], '/alias_for_node_1_und', format_string('The last created alias loaded by default.'));
+    $this->assertEqual($loadedAlias['alias'], '/alias_for_node_1_und', 'The last created alias loaded by default.');
 
     //Update a few aliases
     foreach ($aliases as $alias) {
diff --git a/core/modules/system/tests/modules/menu_test/src/TestControllers.php b/core/modules/system/tests/modules/menu_test/src/TestControllers.php
index f3ff8d2a3fd87d01292d43090e717c03b45e0ec0..2a91286412ce34cbcd182a848c30e8d873b9ff53 100644
--- a/core/modules/system/tests/modules/menu_test/src/TestControllers.php
+++ b/core/modules/system/tests/modules/menu_test/src/TestControllers.php
@@ -57,7 +57,7 @@ public function testDefaults($placeholder = NULL) {
       return ['#markup' => SafeMarkup::format("Sometimes there is a placeholder: '@placeholder'.", array('@placeholder' => $placeholder))];
     }
     else {
-      return ['#markup' => SafeMarkup::format('Sometimes there is no placeholder.')];
+      return ['#markup' => 'Sometimes there is no placeholder.'];
     }
   }