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_gdbm.rb
    path of file: ./repos/ruby-packer/ruby/test/gdbm
    
    the code of the file until where you have to start completion: # frozen_string_literal: false
begin
  require 'gdbm'
rescue LoadError
end

if defined? GDBM
  require 'test/unit'
  require 'envutil' unless defined?(EnvUtil)
  require 'tmpdi
    
    def test_invert
      v = "0"
      100.times {@gdbm[v] = v; v = v.next}

      hash = @gdbm.invert
      assert_instance_of(Hash, hash)
      assert_equal(100, hash.size)
      hash.each_pair {|key, val|
        assert_equal(key.to_i, val.to_i)
      }
    end