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\n​zzz,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\n​value1,value2,value3​\r\n​"​)).

It is also a more visual representation of the meaning of the content.