refactoring

process.rb

def process_mdn(mdn)

  return "0" if mdn.nil? || mdn.length != 10

  unless mdn.nil?
    mdn = mdn[1..-1] #remove the leading "1"
  else
    "0"
  end

  unless mdn.length != 10
    mdn
  else
    "0"
  end

end

process_spec.rb

describe "process" do
  it "returns a '0' when the mdn is nil" do
    process_mdn(nil).should == "0"
    process_mdn().should == "0"
  end

  it "returns '1234567890' when the mdn is '1234567890" do
    mdn = '1234567890'
    process_mdn(mdn).should == '1234567890'
  end
end