--- /dev/null
+<?php
+
+namespace Drupal\plugin_test\Plugin\plugin_test\mock_block;
+
+use Drupal\Component\Plugin\PluginBase;
+
+/**
+ * Mock implementation of a test block plugin used by Plugin API unit tests.
+ *
+ * @see \Drupal\plugin_test\Plugin\DefaultsTestPluginManager
+ */
+class MockTestBlock extends PluginBase {
+
+}