--- /dev/null
+<?php
+
+namespace Drupal\simpletest;
+
+use Drupal\Component\Render\MarkupInterface;
+
+/**
+ * Provides helper methods for assertions.
+ */
+trait AssertHelperTrait {
+
+ /**
+ * Casts MarkupInterface objects into strings.
+ *
+ * @param string|array $value
+ * The value to act on.
+ *
+ * @return mixed
+ * The input value, with MarkupInterface objects casted to string.
+ */
+ protected static function castSafeStrings($value) {
+ if ($value instanceof MarkupInterface) {
+ $value = (string) $value;
+ }
+ if (is_array($value)) {
+ array_walk_recursive($value, function (&$item) {
+ if ($item instanceof MarkupInterface) {
+ $item = (string) $item;
+ }
+ });
+ }
+ return $value;
+ }
+
+}