Best Logic to Set Up and A/B Test Nurture Journeys

Hello Marketo Community,

We are working on a campaign and would like to A/B test 2 journeys. We have the journeys set up as two different streams in our nurture program but aren't sure what the best way would be to randomly add users to one stream vs another and automate the process.

Right now the idea we are going off is to have 1 stream get feed contacts for one week's time, and then have another be feed contacts for the week that follows. Then we analyze both of these sets of users and see what journey performed best.

I'm curious to see how others have accomplished this in the past and want to know if there are other, more effective or fully automated, ways to do this that we haven't thought of yet.