zip_extractor.rb

class ZipExtractor
  def initialize(source_path)
    @unzipped = false
    @source_path = source_path
  end

  ##
  # unzip the export and return the list of files in it
  def extracted_file_list
    unzip unless @unzipped
    Dir[File.join(target_directory, "*")]
  end

  private

  # The directory to unzip the download to
  def target_directory
    Rails.root.join("tmp", "product_catalog_export")
  end

  def unzip
    FileUtils.rm_rf(target_directory) # delete old export

    # unzip the latest export
    Zip::File.open(@source_path) do |zip_file|
      zip_file.each do |f|
        f_path = File.join(target_directory, f.name)
        FileUtils.mkdir_p(File.dirname(f_path))
        zip_file.extract(f, f_path) unless File.exist?(f_path)
      end
    end

    @unzipped = true
  end
end

zip_extractor_spec.rb

RSpec.describe Salesforce::XmlData::CatalogExport::ZipExtractor do
  describe '#extracted_file_list' do
    # subject / inputs
    let(:source_zip_path) { Rails.root.join("tmp", "some_zip_file.zip") }
    subject { described_class.new(source_zip_path) }

    # mock  objects
    let(:file1) { instance_double("Zip::Entry", name: "file1.xml") }
    let(:file2) { instance_double("Zip::Entry", name: "file2.xml") }
    let(:zip_file) { instance_double("Zip::File") }
    let(:extracted_file_list) { ['file1.xml', 'file2.xml']}

    before do
      # stubs
      expect(FileUtils).to receive(:rm_rf)
      expect(FileUtils).to receive(:mkdir_p).twice
      expect(Zip::File).to receive(:open).and_yield(zip_file)
      expect(zip_file).to receive(:each).and_yield(file1).and_yield(file2)
      expect(zip_file).to receive(:extract).twice
      expect(Dir).to receive(:[]).and_return(extracted_file_list)
    end

    it 'returns a list of files in a zip file' do
      expect(subject.extracted_file_list).to eq(extracted_file_list)
    end
  end
end