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_set_len.rb
    path of file: ./repos/jruby/test/mri/-ext-/string
    
    the code of the file until where you have to start completion: # frozen_string_literal: false
require 'test/unit'
require "-test-/string"

class Test_StrSetLen < Test::Unit::TestCase
  def setup
    @s0 = [*"a".."z"].join("").freeze
    @s1 = Bug::String.new(@s0)
  end

  
    
  def test_capacity_equals_to_new_size
    bug12757 = "[ruby-core:77257] [Bug #12757]"
    # fill to ensure capacity does not decrease with force_encoding
    str = Bug::String.new("\x00" * 128, capacity: 128)
    str.force_encoding("UTF-32BE")
    assert_equal 128, Bug::String.capacity(str)
    assert_equal 127, str.set_len(127).bytesize, bug12757
  end
end