I get the following when using check50 for caesar.

:) caesar.c exists
:) caesar.c compiles
:) encrypts "a" as "b" using 1 as key
:( encrypts "barfoo" as "yxocll" using 23 as key
    \ expected output, but not "yx��c����\n"
:) encrypts "BARFOO" as "EDUIRR" using 3 as key
:) encrypts "BaRFoo" as "FeVJss" using 4 as key
:) encrypts "barfoo" as "onesbb" using 65 as key
:( encrypts "world, say hello!" as "iadxp, emk tqxxa!" using 12 as key
    \ expected output, but not "��adxp, em�� tqxxa!\n"
:) handles lack of argv[1]

Obviously it is the :( that have me confused. I believe I have the correct output format, with the first line being the program name and key, the next line the message to cipher and the last line the encrypted message with no additional text.

Thank you