gistfile1.txt

require 'rubygems'
require 'rest-assured'

RestAssured::Double.create(fullpath: '/products', content: 'this is content')

---
gives me...
---

/Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:588:in `prefix': undefined method `path' for nil:NilClass (NoMethodError)
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:598:in `prefix_source'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:952:in `prefix_parameters'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:967:in `block in split_options'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:965:in `each'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:965:in `split_options'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:1454:in `split_options'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:1257:in `load'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:1007:in `initialize'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:747:in `new'
        from /Users/starls01/.rvm/gems/ruby-1.9.3-p125/gems/activeresource-3.2.3/lib/active_resource/base.rb:747:in `create'
        from test.rb:4:in `<main>'

Dunno if you ever found the answer, but I just stumbled across this randomly while searching for a different problem and if you are still wondering about this then you need to call start() first before you can create any doubles.

eg:

RestAssured::Server.start(:database => ':memory:')`

(It's not a great error message, is it... 😄)