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_source_list.rb
    path of file: ./repos/jruby/test/mri/rubygems
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
require 'rubygems'
require 'rubygems/source_list'
require_relative 'helper'

class TestGemSourceList < Gem::TestCase
  def setup
    super

    @uri = "http://ex
    
  def test_append
    sl = Gem::SourceList.new
    sl << @uri
    sl << @uri

    assert_equal sl.to_a.size, 1

    sl.clear
    source = (sl << @uri)

    assert_kind_of Gem::Source, source

    assert_kind_of URI, source.uri
    assert_equal source.uri.to_s, @uri

    assert_equal [source], sl.sources
  end