Escaped Mutant for Mutator "Concat": --- Original +++ New @@ @@ private static function getFromContainer(string $class) : object { // Check if container is set - self::$container === null and throw new ConfigurationException(\sprintf('Container has not been set. Please set the container first using %s method.', self::class . '::setContainer()')); + self::$container === null and throw new ConfigurationException(\sprintf('Container has not been set. Please set the container first using %s method.', '::setContainer()' . self::class)); // Pull service from container try { return self::$container->get($class);