In order to do A/B testing with automated Messages, you must create a Message2 and inside this Message2, create 2 versions.
Version 1 : You indicate « Contact.idContact % 2 == 0 » in field « Condition ».
Version 2 : You put nothing in field « Condition ».
This will alternate sendings between version 1 and version 2 of the Message, allowing to separate the sending between the two versions on the targeted group.
Warning : As this feature is rarely used, our interfaces do not directly provide the tools which will represent the results (by versions) in a graphical way. But, you can easily retireve "Raw statistics" in the Daily CSVs exports that are in place for your account.