尝试测试嵌套属性时Rspec抛出的未知属性错误

I have built an application based on the Hartl course - up to and including section 9.2 (authentication). From there I have tried to extend the functionality by adding in an Organization model. Initially I tried using the scaffold generate command line function, decided it had built too much, rolled it back and then built it by hand. I believe in this mess I may have screwed up my migrations (see below). I'm using Rails v4.1.1, Rspec 3.0.0 and Capybara 2.2.0 - all databases are postgres.I have built an application based on the Hartl