diff --git a/tests/phpunit/includes/class-jsonserializable-object.php b/tests/phpunit/includes/class-jsonserializable-object.php
new file mode 100644
index 0000000000..eb4ae5c3af
--- /dev/null
+++ b/tests/phpunit/includes/class-jsonserializable-object.php
@@ -0,0 +1,21 @@
+<?php
+/**
+ * Unit Tests: JsonSerializable_Object
+ *
+ * @package WordPress
+ * @subpackage UnitTests
+ * @since 5.3.0
+ */
+
+class JsonSerializable_Object implements JsonSerializable {
+
+	private $data;
+
+	public function __construct( $data ) {
+		$this->data = $data;
+	}
+
+	public function jsonSerialize() {
+		return $this->data;
+	}
+}