test.rb

require 'sprockets'
require 'stackprof'
require 'tmpdir'
require 'fileutils'
require 'allocation_tracer'
require 'minitest/autorun'

Class.new(Minitest::Test) do
  attr_reader :path, :environment, :env, :n

  def setup
    @path = Dir.mktmpdir
    @pwd = Dir.pwd
    Dir.chdir @path

    js_dir = File.join path, 'app', 'assets', 'javascripts'
    js_contents = "function test() { }"
    FileUtils.mkdir_p js_dir
    File.open(File.join(js_dir, 'test.js'), 'w') { |f|
      f.write js_contents
    }

    # sanity check
    assert_equal js_contents, File.read(File.join(js_dir, 'test.js'))

    @env = {
      "REQUEST_METHOD" => "GET",
      "QUERY_STRING" => "body=1",
      "PATH_INFO" => "test.js"
    }
    @environment = Sprockets::Environment.new
    @environment.append_path 'app/assets/javascripts'
    @n = 5000
  end

  def teardown
    Dir.chdir @pwd
    FileUtils.remove_entry @path
  end

  def test_allocations
    ObjectSpace::AllocationTracer.setup(%i{path line type})
    result = ObjectSpace::AllocationTracer.trace {
      n.times { |i|
        status, headers, body = environment.call env
        body.each { |x| x }
      }
    }
    result.sort_by { |k,v| v.first }.each do |k,v|
      p k => v
    end
  end

  def test_runtime
    StackProf.run(mode: :wall, out: 'out.dump') do
      n.times { |i|
        status, headers, body = environment.call env
        body.each { |x| x }
      }
    end
    system "stackprof out.dump"
  end
end