I had starting to read your book. Seems a good book, actually a needed book to help improving the rails practice. I just had actually read the first chapter and skim the others. But IMHO you can improve the book if you reorganized the chapters and materials to follow the outside-in cycle: starting with business facing scenarios (acceptance test - plain-text functional descriptions in Cucumber) and working our way inward to the underlying objects (unit/functional test with Test::Unit/RSpec/Shoulda), as you know outside-in is key for BDD. As it is mentioned in the Rspec Book: “Outside-in Rails development” means starting with views and working our way in towards the models. This approach lets customer-defined acceptance criteria drive development, and puts us in a position to discover objects and interfaces earlier on in the process and make design decisions based on real need. Why this matters? Well because as developers we want and need to produce business value for our costumers/stakeholders and one of the most effective ways currently use is the outside-in cycle. I think that this will help to have a very clear driving force that is to produce business value.