--- /dev/null
+<?php
+
+namespace Drupal\file_test\StreamWrapper;
+
+use Drupal\Core\StreamWrapper\LocalReadOnlyStream;
+
+/**
+ * Helper class for testing the stream wrapper registry.
+ *
+ * Dummy stream wrapper implementation (dummy-readonly://).
+ */
+class DummyReadOnlyStreamWrapper extends LocalReadOnlyStream {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function getName() {
+ return t('Dummy files (readonly)');
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function getDescription() {
+ return t('Dummy wrapper for simpletest (readonly).');
+ }
+
+ public function getDirectoryPath() {
+ return \Drupal::service('site.path') . '/files';
+ }
+
+ /**
+ * Override getInternalUri().
+ *
+ * Return a dummy path for testing.
+ */
+ public function getInternalUri() {
+ return '/dummy/example.txt';
+ }
+
+ /**
+ * Override getExternalUrl().
+ *
+ * Return the HTML URI of a public file.
+ */
+ public function getExternalUrl() {
+ return '/dummy/example.txt';
+ }
+
+}