invalid1.txt: signature without a= tag is invalid
invalid2.txt: signature with v= tag is invalid
invalid3.txt: signature without b= tag is invalid
invalid4.txt: signature without b= content is invalid
invalid5.txt: signature with truncated b= content should fail verification
invalid6.txt: signature without d= tag is invalid
invalid7.txt: d= tag contains nonexistent domain
invalid8.txt: signature without h= tag is invalid
invalid9.txt: signature without s= tag is invalid

test0.txt: standard signature (no modifications)
test1.txt:
test2.txt: contents of h= tag are case insensitive
test3.txt: tests different order of tags
test4.txt: tests whitespace inserted within b= tag (after signing)
test5.txt: DKIM-Signature header name is case insensitive
test6.txt: d= and s= tag contents are case insensitive
test7.txt: tests whitespace within h= tag
test8.txt: unrecognized tags