gistfile1.txt

/vagrant/test_spec.rb:3:in `block in <top (required)>': undefined local variable or method `foo' for #<Class:0x000000020035c8> (NameError)
  from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/example_group.rb:244:in `module_eval'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/example_group.rb:244:in `subclass'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/example_group.rb:230:in `describe'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/dsl.rb:18:in `describe'
	from /vagrant/test_spec.rb:1:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/configuration.rb:789:in `load'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/configuration.rb:789:in `block in load_spec_files'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/configuration.rb:789:in `each'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/configuration.rb:789:in `load_spec_files'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/command_line.rb:22:in `run'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/runner.rb:80:in `run'
	from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/rspec-core-2.12.1/lib/rspec/core/runner.rb:17:in `block in autorun'

test_spec.rb

describe "test" do
  let(:foo) { double('my test', bar: "hooray") }
  describe "i can access let vars: #{foo.bar}"
end

also you could do:

shared_example 'pass the var' do |target|
  it { public_send(target).should eq 'test' }
end

describe 'test' do
  let(:foo) { 'test' }

  it_behaves_like 'pass the var' :foo
end