old_contents: require('proof')(3, require('cadence')(prove))
  
  function prove (async, assert) {
      var UserAgent = require('../..')
      var Transport = require('../../mock')
      var responses = [
          function (request, response, next) {
              response.writeHead(200, 'ignore', { key: 'value' })
              response.end('foo')
              assert(response.getHeader('key'), 'value', 'get header')
              next()
          },
          function (request, response, next) {
              response.writeHead(200)
              response.end('foo')
              next()
          }
      ]
      var transport = new Transport(function (request, response, next) {
          responses.shift()(request, response, next)
      })
      var ua = new UserAgent({ transport: transport })
      async(function () {
          ua.fetch({ url: '/' }, async())
      }, function (body, response, buffer) {
          assert(response.headers, { key: 'value' }, 'headers')
          ua.fetch({ url: '/' }, async())
      }, function (body, response, buffer) {
          assert(response.headers, {}, 'no headers')
      })
  }
  
new_contents: require('proof')(3, require('cadence')(prove))
  
  function prove (async, assert) {
      var UserAgent = require('../..')
      var Transport = require('../../mock')
      var responses = [
          function (request, response, next) {
              response.writeHead(200, 'ignore', { key: 'value' })
              response.end('foo')
              assert(response.getHeader('key'), 'value', 'get header')
          },
          function (request, response, next) {
              response.writeHead(200)
              response.end('foo')
          }
      ]
      var transport = new Transport(function (request, response, next) {
          responses.shift()(request, response, next)
      })
      var ua = new UserAgent({ transport: transport })
      async(function () {
          ua.fetch({ url: '/' }, async())
      }, function (body, response, buffer) {
          assert(response.headers, { key: 'value' }, 'headers')
          ua.fetch({ url: '/' }, async())
      }, function (body, response, buffer) {
          assert(response.headers, {}, 'no headers')
      })
  }
  
subject: Fix `mock.t.js`.