Zhège xiàngmù jiāng chéngwéi wǒmen jìshù de shìjīnshí.
This project will be the acid test of our technology.
Tips
culture
Originally a real object: a black siliceous stone against which jewellers rubbed gold to judge its purity by the streak it left. The figurative 'reliable test' sense tracks the Western use of 'touchstone' exactly.