diff --git a/core/modules/system/src/Tests/Image/ToolkitGdTest.php b/core/modules/system/src/Tests/Image/ToolkitGdTest.php
index 17aeeab..7d4a7c6 100644
--- a/core/modules/system/src/Tests/Image/ToolkitGdTest.php
+++ b/core/modules/system/src/Tests/Image/ToolkitGdTest.php
@@ -278,9 +278,19 @@ function testManipulations() {
           }
         }
 
+        // Store the original GD resource.
+        $old_res = $toolkit->getResource();
+
         // Perform our operation.
         $image->apply($values['function'], $values['arguments']);
 
+        // If the operation replaced the resource, check that the old one has
+        // been destroyed.
+        $new_res = $toolkit->getResource();
+        if ($new_res !== $old_res) {
+          $this->assertFalse(is_resource($old_res), SafeMarkup::format("'%operation' destroyed the original resource.", ['%operation' => $values['function']]));
+        }
+
         // To keep from flooding the test with assert values, make a general
         // value for whether each group of values fail.
         $correct_dimensions_real = TRUE;