Is it possible to write a self-test for a module that depends on user input?

Is it possible to write a self-test for a module that depends on user input, or is it usually not performed, because the probability of a user error during input is too high?

Edit:

Suppose I have a function that returns Hello Worldwhen the user clicks on up_key- then before testing the consequences of an incorrect keystroke, I would like to check if the function really returns Hello Worldif up_key.