What does Genesis 42:7 mean?

As soon as Joseph saw his brothers, he recognized them, but he acted like a stranger and spoke harshly. He asked, 'Where are you from?' They answered, 'We're from Canaan. We've come to buy food.' Genesis 42:7 - Modern Text Bible

(Joseph knows who they are, but they have no idea who he is. He keeps his identity hidden and tests them.)