--- /dev/null
+<?php
+
+namespace Drupal\Core\Test;
+
+use Drupal\Core\Cache\Cache;
+
+/**
+ * Provides a method to refresh in-memory configuration and state information.
+ */
+trait RefreshVariablesTrait {
+
+ /**
+ * Refreshes in-memory configuration and state information.
+ *
+ * Useful after a page request is made that changes configuration or state in
+ * a different thread.
+ *
+ * In other words calling a settings page with $this->drupalPostForm() with a
+ * changed value would update configuration to reflect that change, but in the
+ * thread that made the call (thread running the test) the changed values
+ * would not be picked up.
+ *
+ * This method clears the cache and loads a fresh copy.
+ */
+ protected function refreshVariables() {
+ // Clear the tag cache.
+ \Drupal::service('cache_tags.invalidator')->resetChecksums();
+ foreach (Cache::getBins() as $backend) {
+ if (is_callable([$backend, 'reset'])) {
+ $backend->reset();
+ }
+ }
+
+ \Drupal::service('config.factory')->reset();
+ \Drupal::service('state')->resetCache();
+ }
+
+}