_kincom.rb

class KincomValidator

  def initialize(file, options)
    @file = file
    @options = options
  end

  def validate
    is_file_valid?
    is_options_valid?
  end

  private
  def is_file_valid?
    validate_file_extension
  end

  def is_options_valid?
    validate_options_hash
    validate_begin_percentage(@options[:begin_percentage])
    validate_prestress(@options[:prestress])
    validate_stop_index(@options[:stop_index])
    validate_arm(@options[:arm])
    validate_name(@options[:name])
    validate_time_values(@options[:time_values])
  end

  def validate_file_extension
    if @file.class.extname(@file) != '.xlsx'
      raise ArgumentError, 'File-type is wrong. Can only read .xlsx files.'
    end
  end

  def validate_options_hash
    @options.each do |key, value|
      if key.nil? || value.nil?
        raise ArgumentError, "The options_hash contains a nil. Shouldn't, really."
      end
    end
  end

  def validate_begin_percentage(begin_percentage)
    if !begin_percentage.is_a? Float
      raise ArgumentError, "Begin percentage: '#{begin_percentage}' must be a Float. It is a #{begin_percentage.class}."
    end
    if begin_percentage <= 0 || begin_percentage >= 1
      raise ArgumentError, 'Begin percentage must be between 0 and 1'
    end
  end

  def validate_prestress(prestress)
    if !prestress.is_a? Float
      raise ArgumentError, "Prestress: '#{prestress}' must be a Float. It is a #{prestress.class}."
    end
  end

  def validate_stop_index(stop_index)
    if !stop_index.is_a? Float
      raise ArgumentError, "Stop_index: '#{stop_index}' must be a Float. It is a #{stop_index.class}."
    end
    if stop_index <= 0 || stop_index >= 1
      raise ArgumentError, 'Stop_index must be between 0 and 1'
    end
  end

  def validate_arm(arm)
    if !arm.is_a? Float
      raise ArgumentError, "Arm: '#{arm}' must be a Float. It is a #{arm.class}."
    end
  end

  def validate_name(name)
    if !name.is_a? String
      raise ArgumentError, "Name: '#{name}' must be a String. It is a #{name.class}."
    end
  end

  def validate_time_values(time_values)
    if time_values != time_values.sort
      raise ArgumentError, 'Time values should be of ascending sizes'
    end
  end
end

error

ERROR["test_kincom", TestXercise, 0.0009512920223642141]
 test_kincom#TestXercise (0.00s)
NoMethodError:         NoMethodError: undefined method `is_file_valid?' for KincomValidator:Module
            D:/Arbejde/ResearchLab/Plugin/xercise/validation/_kincom.rb:4:in `validate'
            D:/Arbejde/ResearchLab/Plugin/xercise/xercise.rb:12:in `kincom'
            D:/Arbejde/ResearchLab/Plugin/myowntest/test_xerciseclass/xercise_test.rb:11:in `test_kincom'

validation_helper.rb

require_relative '_kincom'

module ValidationHelper
  def self.kincom
    include KincomValidator
  end

end

xercise.rb

require_relative './validation/validation_helper.rb'

module Xercise

  def self.kincom(file, options)
    ValidationHelper.kincom
    KincomValidator.validate(file, options)
  end

end