rails--rails/actionpack/test/controller/api/data_streaming_test.rb

require 'abstract_unit'

module TestApiFileUtils
  def file_path() File.expand_path(__FILE__) end
  def file_data() @data ||= File.open(file_path, 'rb') { |f| f.read } end
end

class DataStreamingApiController < ActionController::API
  include TestApiFileUtils

  def one; end
  def two
    send_data(file_data, {})
  end
end

class DataStreamingApiTest < ActionController::TestCase
  include TestApiFileUtils
  tests DataStreamingApiController

  def test_data
    response = process('two')
    assert_kind_of String, response.body
    assert_equal file_data, response.body
  end
end