Obviousness tests derive entirely from the federal courts. The law (35 USC 103) itself is rather concise (http://www.uspto.gov/web/offices/pac/mpep/documents/a

Obviousness tests derive entirely from the federal courts. The law (35 USC 103) itself is rather concise (http://www.uspto.gov/web/offices/pac/mpep/documents/appxl_35_U_S_C_103.htm http://www.uspto.gov/web/offices/pac/mpep/documents/appxl_35...): A patent will not be granted if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art to which said subject matter pertains. The federal courts have interpreted this sentence into various tests over the years, which are then interpreted further into guidelines set forth by the USPTO.