.rb

require 'rails_helper'

describe CsvHandler::TotalRevenue do
  describe '#total_revenue' do

    before do
      @import = CsvHandler::ImportData.new('public', 'purchases.csv')
      @import.import
      @revenue = CsvHandler::TotalRevenue.new('public', 'purchases.csv')
    end

    context 'given a purchase file' do
      it 'calculates total revenue and updates db' do
        expect{ @revenue.total_revenue }.to change(Import.last, :total_revenue)
      end
    end
  end
end

module CsvHandler
  class ImportData
    def initialize(file_path, file_name)
      @path = file_path
      @filename = file_name
    end

    def import
      file_path = PathJoiner::PathJoiner.join_path(@path, @filename)
      @import = Import.create
      CSV.foreach(file_path, headers: true) do |row|
        @import.purchases.create(row.to_hash)
      end
    end
  end
end