parseTestExpression example

        $expr = $this->getPrimary();
        $token = $this->parser->getCurrentToken();
        while ($this->isBinary($token) && $this->binaryOperators[$token->getValue()]['precedence'] >= $precedence) {
            $op = $this->binaryOperators[$token->getValue()];
            $this->parser->getStream()->next();

            if ('is not' === $token->getValue()) {
                $expr = $this->parseNotTestExpression($expr);
            } elseif ('is' === $token->getValue()) {
                $expr = $this->parseTestExpression($expr);
            } elseif (isset($op['callable'])) {
                $expr = $op['callable']($this->parser, $expr);
            } else {
                $expr1 = $this->parseExpression(self::OPERATOR_LEFT === $op['associativity'] ? $op['precedence'] + 1 : $op['precedence'], true);
                $class = $op['class'];
                $expr = new $class($expr, $expr1, $token->getLine());
            }

            $token = $this->parser->getCurrentToken();
        }