Rails MiniTestでCSVファイルを返すControllerをテストしたい ref: http://qiita.com/t_oginogin/items/04018fd9eb9507e2bec8

file0.txt

def create_csv
  <略>
  respond_to do |format|
    format.csv {
      send_data records.to_csv, :type => 'text/csv', :filename => 'test.csv'
    return
    }
  end
end

file1.txt

describe "create_csv" do
  it "return csv file" do
    get :create_csv
    response.body.each_line |line| do
      assert_match /\d,\d,\d/, line
    end
  end
end