diff -u b/core/modules/image/lib/Drupal/image/Tests/ImageStyleFlushTest.php b/core/modules/image/lib/Drupal/image/Tests/ImageStyleFlushTest.php
--- b/core/modules/image/lib/Drupal/image/Tests/ImageStyleFlushTest.php
+++ b/core/modules/image/lib/Drupal/image/Tests/ImageStyleFlushTest.php
@@ -101,8 +101,8 @@
     // forces an image style flush.
     $style_path = 'admin/config/media/image-styles/manage/' . $style->id();
     $ieids = array();
-    foreach ($style->effects as $ieid => $effect) {
-      $ieids[$effect['id']] = $ieid;
+    foreach ($style->getEffects() as $ieid => $effect) {
+      $ieids[$effect->getPluginId()] = $ieid;
     }
     $this->drupalPost($style_path . '/effects/' . $ieids['image_scale'] . '/delete', array(), t('Delete'));
     $this->assertResponse(200);