Rails version clarification

I'm currently working out of the book Agile Web Development with Rails (Fourth edition) and it instructs users to use rails version 3.2.0.

I am getting an error when running "rake test" (see below)
http://ift.tt/1NhSFRi

After doing some looking around, it appears that this is a bug caused by my rails version.

I would like to fix this massive error dump, but it seems my only answer is to change rails version. I'd like to know if its safe to do so, or if there is a fix I didn't know about.

Thanks!