only in patch2:
unchanged:
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigExportImportUITest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigExportImportUITest.php
@@ -127,6 +127,23 @@ public function testExportImport() {
 
     $this->assertEqual(\Drupal::config('system.site')->get('slogan'), $this->newSlogan);
 
+    $this->assertText('Changes have been made to your active configuration, which might be lost on the next import attempt. ' .
+      'You can find and review the differences between snapshot and active/staging storage here');
+
+    $changedSlogan = $this->randomString(16);
+
+    \Drupal::config('system.site')
+      ->set('slogan', $changedSlogan)
+      ->save();
+
+    $this->clickLink('Compare snapshot and active/staging storage');
+    $this->assertText('View changes between snapshot and active configuration');
+    $this->assertText('system.site');
+    $this->assertText('Active storage');
+    $this->assertText($changedSlogan, 'Changed slogan found on when viewing changes.');
+    $this->clickLink('Compare snapshot with staging storage');
+    $this->assertText('View changes between snapshot and staging configuration');
+
     $this->drupalGet('node/add');
     $this->assertFieldByName("{$this->field->name}[0][value]", '', 'Widget is displayed');
   }