At least in writing your attitude sucks. Hopefully youre nicer on the phone.
As to how normal it is; only once have I been asked to do something exceptional before interview, and when I met it they offered me the position. A date is a date, and if they want anything more then you have the upper hand. Dont be an ass about it, but try your best to meet their expectations. If the employer isnt good enough for you then you dont have to take it.
My general advice is just try your best. Everyone likes a tryer.
As to how normal it is; only once have I been asked to do something exceptional before interview, and when I met it they offered me the position. A date is a date, and if they want anything more then you have the upper hand. Dont be an ass about it, but try your best to meet their expectations. If the employer isnt good enough for you then you dont have to take it.
My general advice is just try your best. Everyone likes a tryer.