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_heuristics.rb
    path of file: ./repos/linguist/test
    
    the code of the file until where you have to start completion: require_relative "./helper"

class TestHeuristics < Minitest::Test
  include Linguist

  def fixture(name)

    
  def test_all_extensions_are_listed
    Heuristics.all.all? do |rule|
      rule.languages.each do |lang|
        unlisted = rule.extensions.reject { |ext| lang.extensions.include? ext }
        assert_equal [], unlisted, (<<~EOF).chomp
          The extension '#{unlisted.first}' is not assigned to #{lang.name}.
          Add it to `languages.yml` or update the heuristic which uses it
        EOF
      end
    end
  end