Hi Vicky,
If I understand the question, you want to be in all of the streams in the same nurture program? One of the great features of the nurture is that the lead can only be in one stream at a time within the program. They can be in multiple programs, but can only be a member of one stream.
What are you looking to test? You can test the content separately or if this isn't active yet you could do testing with accelerated cadences (https://community.marketo.com/MarketoArticle?id=kA050000000LB9CCAW). Or if you really wanted to be in all streams, I'd maybe split up the seed list.
Thanks,
Kim