diff -u b/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php b/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php
--- b/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php
@@ -67,21 +67,11 @@
    * Data provider for testSet().
    */
   public function providerSet() {
-    // Checks that invalid multi-byte sequences are escaped.
-    $tests[] = array(
-      'Foo�barbaz',
-      'Invalid sequence "Foo\xC0barbaz" is escaped',
-      TRUE
-    );
     $tests[] = array(
       "Fooÿñ",
-      'SafeMarkup::set() does not escape valid sequence "Fooÿñ"'
-    );
-    $tests[] = array(
-      new TextWrapper("Fooÿñ"),
-      'SafeMarkup::set() does not escape valid sequence "Fooÿñ" in an object implementing __toString()'
+      'SafeMarkup::setMultiple() does not escape valid sequence "Fooÿñ"'
     );
-    $tests[] = array("<div>", 'SafeMarkup::set() does not escape HTML');
+    $tests[] = array("<div>", 'SafeMarkup::setMultiple() does not escape HTML');
 
     return $tests;
   }
@@ -98,7 +88,7 @@
    * @covers ::setMultiple
    */
   public function testSet($text, $message) {
-    SafeMarkup::setMultiple([(string) $text => ['html' => TRUE]]);
+    SafeMarkup::setMultiple([$text => ['html' => TRUE]]);
     $this->assertTrue(SafeMarkup::isSafe($text), $message);
   }