I noticed that the author uses sequences of the same letters for testing.
rfc_record_per_line_test() ->
?assertEqual([#{"aaa" => "zzz", "bbb" => "yyy", "ccc" => "xxx"}],
bday_csv:decode("aaa,bbb,ccc\r\nzzz,yyy,xxx\r\n")).
Note that sequences of different letters plus numbers can help to detect possible hidden errors when rearranging characters during decoding:
rfc_record_per_line_test() ->
?assertEqual([#{"title1" => "value1", "title2" => "value2", "title3" => "value3"}],
bday_csv:decode("title1,title2,title3\r\nvalue1,value2,value3\r\n")).
It is also a more visual representation of the meaning of the content.