Let not working in scope of nested describe

spec

require 'helper'

describe ZenGenerator do
  let (:good_attributes) do
    Hash.new(start: 20, finish: 30, prefix: "V", suffix: "X", prefix_zeroes: true)
  end


  describe "Initialization:" do
    describe "#initialize" do
      good_attributes.each do |attr, val|
        it "sets the instance variable for #{attr}" do
          ZenGenerator.new(var: val).send("#{attr}").must_equal val
        end
      end
    end
  end
end