rspec & rails 3 cannot find model object - ruby-on-rails

Question

I'm trying to put some specs around a new rails 3 project I am working on, and my first test doesn't seem to be able to find a model.
I've installed rspec from the command line using:
sudo gem install rspec --pre
and then I put the following in my Gemfile
gem "rspec-rails", ">= 2.0.0.beta.1"
But when I run my test I get
./spec/models/world_spec.rb:1: uninitialized constant World (NameError)
rake aborted!
Command /opt/local/bin/ruby -Ilib -Ispec "./spec/models/world_spec.rb" failed
/opt/local/lib/ruby/gems/1.8/gems/rspec-core-2.0.0.beta.4/lib/rspec/core/rake_task.rb:71:in 'define'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1112:in 'verbose'
/opt/local/lib/ruby/gems/1.8/gems/rspec-core-2.0.0.beta.4/lib/rspec/core/rake_task.rb:57:in 'send'
/opt/local/lib/ruby/gems/1.8/gems/rspec-core-2.0.0.beta.4/lib/rspec/core/rake_task.rb:57:in 'define'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in 'call'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in 'execute'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in 'each'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in 'execute'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in 'invoke_with_call_chain'
/opt/local/lib/ruby/1.8/monitor.rb:242:in 'synchronize'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in 'invoke_with_call_chain'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in 'invoke'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in 'invoke_task'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in 'top_level'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in 'each'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in 'top_level'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in 'standard_exception_handling'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in 'top_level'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in 'run'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in 'standard_exception_handling'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in 'run'
/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/bin/rake:31
/opt/local/bin/rake:19:in 'load'
/opt/local/bin/rake:19
My spec is in spec/models/world_spec.rb, and looks like
describe World, "#hello" do
it "should be invalid" do
World.new.should be_invalid?
end
end
I tried adding a line like require "app/model/world" and require "world" but to no success.
Does anyone know what I'm doing wrong?

Answer 1

Seems in rails 3 I need to require 'spec_helper'
require 'spec_helper'
describe World do
it "should be invalid" do
World.new.should be_invalid?
end
end
But that might just be because I'm running it from rake spec if you're using watchr or some other mechanism you might be able to get that done for you.