class Gem::FakeFetcher

def fetch_size(path)
  path = path.to_s
  @paths << path
  raise ArgumentError, 'need full URI' unless path =~ %r'^http://'
  unless @data.key? path then
    raise Gem::RemoteFetcher::FetchError.new("no data for #{path}", path)
  end
  data = @data[path]
  data.respond_to?(:call) ? data.call : data.length
end