bear in mind that while percent code coverage is lofty goal that we should all strive for percent coverage is not enoughjust because statement was tested does not mean that it was tested properly for all possible inputs case study let' walk through test-driven development by writing smalltestedcryptography application don' worryyou won' need to understand the mathematics behind complicated modern encryption algorithms such as threefish or rsa insteadwe'll be implementing sixteenth-century algorithm known as the vigenere cipher the application simply needs to be able to encode and decode messagegiven an encoding keywordusing this cipher firstwe need to understand how the cipher works if we apply it manually (without computerwe start with table like thisa