interface.rb

# @!visibility private

class Loader
  require_relative 'excel/_kincom'
  require_relative 'excel/_vo2max'
  # Måske flytte error-messages til en seperat fil?
  NEGATIVE = "There is a negative value. That doesn't make sense. Oxygen consumption cannot be negative"
  IS_EMPTY = "The data array is empty. This cannot be good."
  WRONG_FILE = "Excel worksheet is not as expected. Is it the raw output?"

  def initialize(file)
    @file = File.open(file, "r")
    self
  end

  def excel(request)
    raise ArgumentError, "No file has been loaded."  if @file.nil?

    case request
    when :kincom
      KincomLoader.new(@file)
    when :vo2max
      Vo2maxLoader.new(@file)
    else
      raise ArgumentError, "#{request.to_s} is not implemented in the loader module."
    end
  end
end

test.rb

class TestLoading < Minitest::Test
  include TestHelperLoading

  def setup
    @kincom_file = './mockups/kincom/test_file.xlsx'
    @vo2max_file = './mockups/vo2max/test_cosmed.xlsx'
  end

  def test_exceptions
    assert_raises ArgumentError do Loader.new(@kincom_file).excel(:invalid) end;
  end

  def test_interface
    assert_instance_of KincomLoader, Loader.new(@kincom_file).excel(:kincom)
    assert_instance_of Vo2maxLoader, Loader.new(@vo2max_file).excel(:vo2max)
  end
end