[Agent 1.1.2] Add unit test to verify unpack_bundle ruby unzip mechanism

Why is this change needed?
---------
Prior to this change, we didn't have a way to test the "overwrite" logic
in ruby unzip during the fallback mechanism of unpack_bundle method in
DownloadBundle command.

How does it address the issue?
---------
This change adds a unit test to verify if the fallback mechanism works
with a debris file in the deployment archive directory.

test/instance_agent/plugins/codedeploy/unpack_bundle_test.rb

@@ -0,0 +1,121 @@
+require 'test_helper'
+require 'certificate_helper'
+require 'stringio'
+require 'aws/codedeploy/local/deployer'
+
+class UnpackBundleTest < InstanceAgentTestCase
+  include InstanceAgent::Plugins::CodeDeployPlugin
+  def generate_signed_message_for(map)
+    message = @cert_helper.sign_message(map.to_json)
+    spec = OpenStruct.new({ :payload => message })
+    spec.format = "PKCS7/JSON"
+
+    return spec
+  end
+
+  # method to create a local source bundle file as zip
+  def setup_local_file_bundle
+    @local_file_directory = File.join(@root_dir, @deployment_group_id.to_s, 'LocalFileDirectory')
+    FileUtils.rm_rf(@local_file_directory)
+    FileUtils.mkdir_p(@local_file_directory)
+
+    input_filenames = %w(file1.txt file2.txt)
+    input_filenames.each do |filename|
+      File.open(File.join(@local_file_directory, filename), "w") do |f|
+        f.write("content of #{filename}")
+        f.close
+      end
+    end
+    # create the bundle as a local zip file
+    @local_file_location = File.join(@local_file_directory, "bundle.zip")
+    Zip::File.open(@local_file_location, Zip::File::CREATE) do |zipfile|
+      input_filenames.each do |filename|
+        zipfile.add(filename, File.join(@local_file_directory, filename))
+      end
+    end
+  end
+
+  context 'The CodeDeploy Plugin Command Executor' do
+    setup do
+      @test_hook_mapping = {
+          "BeforeBlockTraffic"=>["BeforeBlockTraffic"],
+          "AfterBlockTraffic"=>["AfterBlockTraffic"],
+          "ApplicationStop"=>["ApplicationStop"],
+          "BeforeInstall"=>["BeforeInstall"],
+          "AfterInstall"=>["AfterInstall"],
+          "ApplicationStart"=>["ApplicationStart"],
+          "BeforeAllowTraffic"=>["BeforeAllowTraffic"],
+          "AfterAllowTraffic"=>["AfterAllowTraffic"],
+          "ValidateService"=>["ValidateService"]
+      }
+      @deploy_control_client = mock
+      @command_executor = InstanceAgent::Plugins::CodeDeployPlugin::CommandExecutor.new(
+          {
+              :deploy_control_client => @deploy_control_client,
+              :hook_mapping => @test_hook_mapping
+          })
+      @aws_region = 'us-east-1'
+      InstanceMetadata.stubs(:region).returns(@aws_region)
+    end
+
+    context "when executing a command" do
+      setup do
+        @cert_helper = CertificateHelper.new
+        @deployment_id = SecureRandom.uuid
+        @deployment_group_name = "TestDeploymentGroup"
+        @application_name = "TestApplicationName"
+        @deployment_group_id = "foobar"
+        @command = Aws::CodeDeployCommand::Types::HostCommandInstance.new(
+            :host_command_identifier => "command-1",
+            :deployment_execution_id => "test-execution")
+        @root_dir = '/tmp/codedeploy/'
+        @deployment_root_dir = File.join(@root_dir, @deployment_group_id.to_s, @deployment_id.to_s)
+        @archive_root_dir = File.join(@deployment_root_dir, 'deployment-archive')
+        ProcessManager::Config.config[:root_dir] = @root_dir
+      end
+
+      context "test fallback mechanism in unpack_bundle in DownloadBundle" do
+        setup do
+          setup_local_file_bundle
+
+          # Create a debris file in the deployment-archive directory to simulate Zip::DestinationFileExistsError.
+          # This error will be thrown, if the ruby unzip overwrite option is not enabled and when the @archive_root_dir already has the same file.
+          # With the ruby unzip overwrite fix, the unpack_bundle should succeed even with debris files.
+          FileUtils.rm_rf(@archive_root_dir)
+          FileUtils.mkdir_p(@archive_root_dir)
+          FileUtils.cp(File.join(@local_file_directory, 'file1.txt'), @archive_root_dir)
+
+          # We need to avoid removing @archive_root_dir in the actual logic, to avoid debris file to be deleted.
+          FileUtils.stubs(:rm_rf).with(@archive_root_dir)
+          # This exception will let the unpack_bundle method to use the rubyzip fallback mechanism
+          InstanceAgent::LinuxUtil.expects(:extract_zip)
+              .with(File.join(@deployment_root_dir, 'bundle.tar'), @archive_root_dir)
+              .raises("Exception: System unzip throws exception with non-zero exit code")
+
+          @command.command_name = 'DownloadBundle'
+          @bundle_type = 'zip'
+          @deployment_spec = generate_signed_message_for(
+              {
+                  "DeploymentId" => @deployment_id.to_s,
+                  "DeploymentGroupId" => @deployment_group_id.to_s,
+                  "ApplicationName" => @application_name,
+                  "DeploymentGroupName" => @deployment_group_name,
+                  "Revision" => {
+                      "RevisionType" => "Local File",
+                      "LocalRevision" => {
+                          "Location" => @local_file_location,
+                          "BundleType" => @bundle_type
+                      }
+                  }
+              })
+        end
+
+        should 'execute DownloadBundle command with debris file in deployment-archive' do
+          assert_equal 1, (Dir.entries(@archive_root_dir) - [".", ".."]).size
+          @command_executor.execute_command(@command, @deployment_spec)
+          assert_equal 2, (Dir.entries(@archive_root_dir) - [".", ".."]).size
+        end
+      end
+    end
+  end
+end