--- /dev/null
+<?php
+
+namespace Drupal\Tests\system\Functional\Form;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\TestFileCreationTrait;
+
+/**
+ * Tests proper removal of submitted form values using
+ * \Drupal\Core\Form\FormState::cleanValues() when having forms with elements
+ * containing buttons like "managed_file".
+ *
+ * @group Form
+ */
+class StateValuesCleanAdvancedTest extends BrowserTestBase {
+
+ use TestFileCreationTrait {
+ getTestFiles as drupalGetTestFiles;
+ }
+
+ /**
+ * Modules to enable.
+ *
+ * @var array
+ */
+ public static $modules = ['file', 'form_test'];
+
+ /**
+ * An image file path for uploading.
+ */
+ protected $image;
+
+ /**
+ * Tests \Drupal\Core\Form\FormState::cleanValues().
+ */
+ public function testFormStateValuesCleanAdvanced() {
+
+ // Get an image for uploading.
+ $image_files = $this->drupalGetTestFiles('image');
+ $this->image = current($image_files);
+
+ // Check if the physical file is there.
+ $this->assertTrue(is_file($this->image->uri), "The image file we're going to upload exists.");
+
+ // "Browse" for the desired file.
+ $edit = ['files[image]' => drupal_realpath($this->image->uri)];
+
+ // Post the form.
+ $this->drupalPostForm('form_test/form-state-values-clean-advanced', $edit, t('Submit'));
+
+ // Expecting a 200 HTTP code.
+ $this->assertResponse(200, 'Received a 200 response for posted test file.');
+ $this->assertRaw(t('You WIN!'), 'Found the success message.');
+ }
+
+}