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_uninstall_command.rb
    path of file: ./repos/artichoke/artichoke-backend/vendor/ruby/test/rubygems
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
require_relative 'installer_test_case'
require 'rubygems/commands/uninstall_command'

class TestGemCommandsUninstallCommand < Gem::InstallerTestCas
    
  def test_execute_outside_gem_home
    ui = Gem::MockGemUi.new "y\n"

    gemhome2 = "#{@gemhome}2"

    a_4, = util_gem 'a', 4
    install_gem a_4 , :install_dir => gemhome2

    Gem::Specification.dirs = [@gemhome, gemhome2]

    assert_includes Gem::Specification.all_names, 'a-4'

    @cmd.options[:args] = ['a:4']

    e = assert_raise Gem::InstallError do
      use_ui ui do
        @cmd.execute
      end
    end

    assert_includes e.message, "a is not installed in GEM_HOME"
  end