diff --git a/core/tests/Drupal/Tests/Core/StringTranslation/TranslationWrapperTest.php b/core/tests/Drupal/Tests/Core/StringTranslation/TranslationWrapperTest.php
index 8f99198..91b941d 100644
--- a/core/tests/Drupal/Tests/Core/StringTranslation/TranslationWrapperTest.php
+++ b/core/tests/Drupal/Tests/Core/StringTranslation/TranslationWrapperTest.php
@@ -6,6 +6,7 @@
 
 namespace Drupal\Tests\Core\StringTranslation;
 
+use Drupal\Core\StringTranslation\TranslationInterface;
 use Drupal\Tests\UnitTestCase;
 use Drupal\Core\StringTranslation\TranslationWrapper;
 
@@ -50,17 +51,16 @@ public function errorHandler($error_number, $error_message) {
    * @covers ::__toString
    */
   public function testToString() {
-    $text = new TranslationWrapper('May I have an exception please?');
+    $string = 'May I have an exception please?';
+    $text = new TranslationWrapper($string);
 
-    $translation = $this->getMock('Drupal\Core\StringTranslation\TranslationInterface');
-    $translation->expects($this->any())
-      ->method('translate')
-      ->willReturnCallback(function () {
-        throw new \Exception('Yes you may.');
-      });
-    $text->setStringTranslation($translation);
+    $translation = $this->prophesize(TranslationInterface::class);
+    $translation->translate($string, [], [])->will(function () {
+      throw new \Exception('Yes you may.');
+    });
+    $text->setStringTranslation($translation->reveal());
 
-    set_error_handler(array($this, "errorHandler"));
+    set_error_handler([$this, 'errorHandler']);
     // We want this to trigger an error.
     $result = (string) $text;
     restore_error_handler();