You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: test_gem_commands_update_command.rb
    path of file: ./repos/ruby/test/rubygems
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

require_relative "helper"
require "rubygems/commands/update_command"

class TestGemCommandsUpdateCommand < Gem::TestCase
  def setup
    super
    common_installer_setup

    @cmd = Gem::Commands::UpdateCommand.new

    @cmd.options[:document] = []

    @specs = spec_fetcher do |fetcher|
      fetcher.download "a", 1
      fetcher.download "a", 2
      fetcher.download "a", "3.a"
    end

    @a1_path  = @specs["a-1"].cache_file
    @a2_path  = @specs["a-1"].cache_file
    @a3a_path = @specs["a-3.a"].cache_file
  end

  def test_execute
    spec_fetcher do
    
  def test_execute_system_specific_older_than_minimum_supported_rubygems
    spec_fetcher do |fetcher|
      fetcher.download "rubygems-update", "2.5.1" do |s|
        s.files = %w[setup.rb]
      end
    end

    @cmd.options[:args]          = []
    @cmd.options[:system]        = "2.5.1"

    oldest_version_mod = Module.new do
      def oldest_supported_version
        Gem::Version.new("2.5.2")
      end
      private :oldest_supported_version
    end

    @cmd.extend(oldest_version_mod)

    assert_raise Gem::MockGemUi::TermError do
      use_ui @ui do
        @cmd.execute
      end
    end

    assert_empty @ui.output
    assert_equal "ERROR:  rubygems 2.5.1 is not supported on #{RUBY_VERSION}. The oldest version supported by this ruby is 2.5.2\n", @ui.error
  end