hash.rb

class Hash
  def with_sym_keys
    self.inject({}) { |memo, (k,v)| memo[k.to_sym] = v; memo }
  end
end

hash_spec.rb

require 'spec_helper'

describe Hash do
  describe "#with_sym_keys" do
    it "should replace string keys with symbols" do
      hash = { "a" => 1, "b" => 1 }
      hash.with_sym_keys.should == { :a => 1, :b => 1 }
    end
  end
end