A/B testing of subject lines in engagement streams

[Anonymous]

What's the easiest way to A/B test subject lines in emails within an engagement stream? I read some articles here but couldn't find the answer. 

[Anonymous]

Hey David,
Champion/Challenger emails can do this!

https://community.marketo.com/MarketoArticle?id=kA050000000LGT0CAO

Will

[Anonymous]

Hi David,

If you are using regular emails in your engagement stream, you can use the champion/challenger feature to perform the test.  You cannot use the email program inside the engagement stream, including inside a program.

Thanks,
Cheryl