only in patch2:
unchanged:
--- a/core/tests/Drupal/Tests/Core/UrlTest.php
+++ b/core/tests/Drupal/Tests/Core/UrlTest.php
@@ -235,6 +235,23 @@ public function testToString($urls) {
   }
 
   /**
+   * Tests the __toString() method.
+   *
+   * @param \Drupal\Core\Url[] $urls
+   *   An array of Url objects.
+   *
+   * @depends testUrlFromRequest
+   *
+   * @covers ::__toString
+   */
+  public function testMagicToString($urls) {
+    foreach ($urls as $index => $url) {
+      $path = array_pop($this->map[$index]);
+      $this->assertSame($path, (string) $url);
+    }
+  }
+
+  /**
    * Tests the toArray() method.
    *
    * @param \Drupal\Core\Url[] $urls