diff --git a/app/controllers/dmsf_controller.rb b/app/controllers/dmsf_controller.rb
index 087f48b3..550c7756 100644
--- a/app/controllers/dmsf_controller.rb
+++ b/app/controllers/dmsf_controller.rb
@@ -506,7 +506,7 @@ def email_entries(selected_folders, selected_files)
       raise RedmineDmsf::Errors::DmsfEmailMaxFileSizeError
     end
 
-    zip.files.each do |f|
+    zip.dmsf_files.each do |f|
       # Action
       audit = DmsfFileRevisionAccess.new
       audit.user = User.current
@@ -517,7 +517,7 @@ def email_entries(selected_folders, selected_files)
 
     # Notification
     begin
-      DmsfMailer.deliver_files_downloaded(@project, zip.files, request.remote_ip)
+      DmsfMailer.deliver_files_downloaded @project, zip.dmsf_files, request.remote_ip
     rescue StandardError => e
       Rails.logger.error "Could not send email notifications: #{e.message}"
     end
@@ -540,7 +540,7 @@ def email_entries(selected_folders, selected_files)
   def download_entries(selected_folders, selected_files)
     zip = Zip.new
     zip_entries(zip, selected_folders, selected_files)
-    zip.files.each do |f|
+    zip.dmsf_files.each do |f|
       # Action
       audit = DmsfFileRevisionAccess.new
       audit.user = User.current
@@ -550,7 +550,7 @@ def download_entries(selected_folders, selected_files)
     end
     # Notifications
     begin
-      DmsfMailer.deliver_files_downloaded(@project, zip.files, request.remote_ip)
+      DmsfMailer.deliver_files_downloaded @project, zip.dmsf_files, request.remote_ip
     rescue StandardError => e
       Rails.logger.error "Could not send email notifications: #{e.message}"
     end
@@ -570,7 +570,7 @@ def zip_entries(zip, selected_folders, selected_files)
       folder = DmsfFolder.visible.find_by(id: selected_folder_id)
       raise RedmineDmsf::Errors::DmsfFileNotFoundError unless folder
 
-      zip.add_folder folder, member, folder&.dmsf_folder&.dmsf_path_str
+      zip.add_dmsf_folder folder, member, folder&.dmsf_folder&.dmsf_path_str
     end
     selected_files.each do |selected_file_id|
       file = DmsfFile.visible.find_by(id: selected_file_id)
@@ -581,10 +581,10 @@ def zip_entries(zip, selected_folders, selected_files)
         raise RedmineDmsf::Errors::DmsfAccessError
       end
 
-      zip.add_file file, member, file.dmsf_folder&.dmsf_path_str
+      zip.add_dmsf_file file, member, file.dmsf_folder&.dmsf_path_str
     end
     max_files = Setting.plugin_redmine_dmsf['dmsf_max_file_download'].to_i
-    raise RedmineDmsf::Errors::DmsfZipMaxFilesError if max_files.positive? && zip.files.length > max_files
+    raise RedmineDmsf::Errors::DmsfZipMaxFilesError if max_files.positive? && zip.dmsf_files.length > max_files
 
     zip
   end
diff --git a/lib/redmine_dmsf/dmsf_zip.rb b/lib/redmine_dmsf/dmsf_zip.rb
index ed76684a..ab26874e 100644
--- a/lib/redmine_dmsf/dmsf_zip.rb
+++ b/lib/redmine_dmsf/dmsf_zip.rb
@@ -24,15 +24,20 @@ module RedmineDmsf
   module DmsfZip
     # ZIP
     class Zip
-      attr_reader :files
+      attr_reader :dmsf_files
 
       def initialize
         @temp_file = Tempfile.new(%w[dmsf_zip_ .zip], Rails.root.join('tmp'))
         @zip_file = ::Zip::OutputStream.open(@temp_file)
         @files = []
+        @dmsf_files = []
         @folders = []
       end
 
+      def read
+        File.read @temp_file
+      end
+
       def finish
         @zip_file.close
         @temp_file.path
@@ -42,37 +47,69 @@ def close
         @zip_file.close
       end
 
-      def add_file(file, member, root_path = nil)
-        return if @files.include?(file)
-        unless file&.last_revision && File.exist?(file.last_revision&.disk_file)
+      def add_dmsf_file(dmsf_file, member = nil, root_path = nil, path = nil)
+        unless dmsf_file&.last_revision && File.exist?(dmsf_file.last_revision.disk_file)
           raise RedmineDmsf::Errors::DmsfFileNotFoundError
         end
 
-        string_path = file.dmsf_folder.nil? ? '' : (file.dmsf_folder.dmsf_path_str + File::SEPARATOR)
-        string_path = string_path[(root_path.length + 1)..string_path.length] if root_path
-        string_path += file.formatted_name(member)
+        if path
+          string_path = path
+        else
+          string_path = dmsf_file.dmsf_folder.nil? ? '' : (dmsf_file.dmsf_folder.dmsf_path_str + File::SEPARATOR)
+          string_path = string_path[(root_path.length + 1)..string_path.length] if root_path
+        end
+        string_path += dmsf_file.formatted_name(member)
+
+        return if @files.include?(string_path)
+
         zip_entry = ::Zip::Entry.new(@zip_file, string_path, nil, nil, nil, nil, nil, nil,
-                                     ::Zip::DOSTime.at(file.last_revision.updated_at))
-        @zip_file.put_next_entry(zip_entry)
-        File.open(file.last_revision.disk_file, 'rb') do |f|
+                                     ::Zip::DOSTime.at(dmsf_file.last_revision.updated_at))
+        @zip_file.put_next_entry zip_entry
+        File.open(dmsf_file.last_revision.disk_file, 'rb') do |f|
+          while (buffer = f.read(8192))
+            @zip_file.write buffer
+          end
+        end
+        @files << string_path
+        @dmsf_files << dmsf_file
+      end
+
+      def add_attachment(attachment, path)
+        return if @files.include?(path)
+
+        raise RedmineDmsf::Errors::DmsfFileNotFoundError unless File.exist?(attachment.diskfile)
+
+        zip_entry = ::Zip::Entry.new(@zip_file, path, nil, nil, nil, nil, nil, nil,
+                                     ::Zip::DOSTime.at(attachment.created_on))
+        @zip_file.put_next_entry zip_entry
+        File.open(attachment.diskfile, 'rb') do |f|
           while (buffer = f.read(8192))
-            @zip_file.write(buffer)
+            @zip_file.write buffer
           end
         end
-        @files << file
+        @files << path
       end
 
-      def add_folder(folder, member, root_path = nil)
-        return if @folders.include?(folder)
+      def add_raw_file(filename, data)
+        return if @files.include?(filename)
+
+        zip_entry = ::Zip::Entry.new(@zip_file, filename, nil, nil, nil, nil, nil, nil, ::Zip::DOSTime.now)
+        @zip_file.put_next_entry zip_entry
+        @zip_file.write data
+        @files << filename
+      end
 
-        string_path = folder.dmsf_path_str + File::SEPARATOR
+      def add_dmsf_folder(dmsf_folder, member, root_path = nil)
+        string_path = dmsf_folder.dmsf_path_str + File::SEPARATOR
         string_path = string_path[(root_path.length + 1)..string_path.length] if root_path
         zip_entry = ::Zip::Entry.new(@zip_file, string_path, nil, nil, nil, nil, nil, nil,
-                                     ::Zip::DOSTime.at(folder.modified))
-        @zip_file.put_next_entry(zip_entry)
-        @folders << folder
-        folder.dmsf_folders.visible.each { |subfolder| add_folder(subfolder, member, root_path) }
-        folder.dmsf_files.visible.each { |file| add_file(file, member, root_path) }
+                                     ::Zip::DOSTime.at(dmsf_folder.modified))
+        return if @folders.include?(string_path)
+
+        @zip_file.put_next_entry zip_entry
+        @folders << string_path
+        dmsf_folder.dmsf_folders.visible.each { |folder| add_dmsf_folder(folder, member, root_path) }
+        dmsf_folder.dmsf_files.visible.each { |file| add_dmsf_file(file, member, root_path) }
       end
     end
   end
diff --git a/test/helper_test.rb b/test/helper_test.rb
index 966a5585..95405699 100644
--- a/test/helper_test.rb
+++ b/test/helper_test.rb
@@ -53,10 +53,9 @@ def setup
         [@project1, @project2].each do |prj|
           prj.enable_module! :dmsf
         end
-        Setting.plugin_redmine_dmsf['dmsf_storage_directory'] = File.join('files', ['dmsf'])
+        Setting.plugin_redmine_dmsf['dmsf_storage_directory'] = File.join('files', 'dmsf')
         Setting.plugin_redmine_dmsf['dmsf_webdav_use_project_names'] = nil
         Setting.plugin_redmine_dmsf['dmsf_projects_as_subfolders'] = nil
-        Setting.plugin_redmine_dmsf['dmsf_storage_directory'] = File.join('files', ['dmsf'])
         FileUtils.cp_r File.join(File.expand_path('../fixtures/files', __FILE__), '.'), DmsfFile.storage_path
       end
 
diff --git a/test/unit/lib/redmine_dmsf/dmsf_macros_test.rb b/test/unit/lib/redmine_dmsf/dmsf_macros_test.rb
index 28bf3873..cc3cc440 100644
--- a/test/unit/lib/redmine_dmsf/dmsf_macros_test.rb
+++ b/test/unit/lib/redmine_dmsf/dmsf_macros_test.rb
@@ -29,8 +29,7 @@ class DmsfMacrosTest < RedmineDmsf::Test::HelperTest
   include Rails.application.routes.url_helpers
   include ActionView::Helpers::UrlHelper
 
-  fixtures :dmsf_folders, :dmsf_files, :dmsf_file_revisions, :dmsf_folders, :dmsf_files,
-           :dmsf_file_revisions
+  fixtures :dmsf_folders, :dmsf_files, :dmsf_file_revisions
 
   def setup
     super
diff --git a/test/unit/lib/redmine_dmsf/dmsf_zip_test.rb b/test/unit/lib/redmine_dmsf/dmsf_zip_test.rb
new file mode 100644
index 00000000..85f0110f
--- /dev/null
+++ b/test/unit/lib/redmine_dmsf/dmsf_zip_test.rb
@@ -0,0 +1,95 @@
+# frozen_string_literal: true
+
+# Redmine plugin for Document Management System "Features"
+#
+# Karel Pičman <karel.picman@kontron.com>
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+
+require File.expand_path('../../../../test_helper', __FILE__)
+
+# Plugin tests
+class DmsfZipTest < RedmineDmsf::Test::HelperTest
+  fixtures :dmsf_folders, :dmsf_files, :dmsf_file_revisions, :attachments
+  def setup
+    @zip = RedmineDmsf::DmsfZip::Zip.new
+
+    Setting.plugin_redmine_dmsf['dmsf_storage_directory'] = File.join('files', 'dmsf')
+    FileUtils.cp_r File.join(File.expand_path('../../../../fixtures/files', __FILE__), '.'), DmsfFile.storage_path
+    @dmsf_file1 = DmsfFile.find(1)
+    @dmsf_folder2 = DmsfFolder.find(2)
+    set_fixtures_attachments_directory
+    @attachment4 = Attachment.find(4)
+  end
+
+  def teardown
+    # Delete our tmp folder
+    FileUtils.rm_rf DmsfFile.storage_path
+  rescue StandardError => e
+    Rails.logger.error e.message
+  end
+
+  def test_add_dmsf_file
+    @zip.add_dmsf_file @dmsf_file1
+    assert_equal 1, @zip.dmsf_files.size
+    zip_file = @zip.finish
+    Zip::File.open(zip_file) do |file|
+      file.each do |entry|
+        assert_equal @dmsf_file1.last_revision.name, entry.name
+      end
+    end
+  end
+
+  def test_add_attachment
+    @zip.add_attachment @attachment4, @attachment4.filename
+    assert_equal 0, @zip.dmsf_files.size
+    zip_file = @zip.finish
+    Zip::File.open(zip_file) do |file|
+      file.each do |entry|
+        assert_equal @attachment4.filename, entry.name
+      end
+    end
+  end
+
+  def test_add_raw_file
+    filename = 'data.txt'
+    content = '1,2,3'
+    @zip.add_raw_file filename, content
+    assert_equal 0, @zip.dmsf_files.size
+    zip_file = @zip.finish
+    Zip::File.open(zip_file) do |file|
+      file.each do |entry|
+        assert_equal filename, entry.name
+        assert_equal content, entry.get_input_stream.read
+      end
+    end
+  end
+
+  def test_read
+    @zip.add_dmsf_file @dmsf_file1
+    assert_not_empty @zip.read
+  end
+
+  def test_finish
+    @zip.add_dmsf_file @dmsf_file1
+    zip_file = @zip.finish
+    assert File.exist?(zip_file)
+  end
+
+  def test_close
+    @zip.add_dmsf_file @dmsf_file1
+    assert @zip.close
+  end
+end