anchor.diff:      <div class="mdl-grid">
         <div class="mdl-cell mdl-cell--3-col">
           <div class="mdl-textfield mdl-js-textfield">
  -          <input class="mdl-textfield__input" type="text" #username1 id="username1">
  -          <label class="mdl-textfield__label" for="username1">Trakt.tv username</label>
  +          <input class="mdl-textfield__input" type="text" #username id="username">
  +          <label class="mdl-textfield__label" for="username">Trakt.tv username</label>
           </div>
  +        <button
  +              class="mdl-button mdl-js-button mdl-button--raised mdl-js-ripple-effect"
  +              (click)="addUser(username)">
  +            Find movies
  +        </button>
  +        <ul class="mdl-list">
  +          <li *ngFor="#user of users" class="mdl-list__item">
  +            <span class="mdl-list__item-primary-content">
  +            {{ user }}
  +            </span>
  +          </li>
  +        </ul>
         </div>
         <div class="mdl-cell mdl-cell--3-col">
  -        <div class="mdl-textfield mdl-js-textfield">
  -          <input class="mdl-textfield__input" type="text" #username2 id="username2">
  -          <label class="mdl-textfield__label" for="username2">Another username</label>
  -        </div>
  -      </div>
  -      <div class="mdl-cell mdl-cell--3-col">
  -        <div class="mdl-textfield mdl-js-textfield">
  -          <input class="mdl-textfield__input" type="text" #username3 id="username3">
  -          <label class="mdl-textfield__label" for="username3">Another (optional) username</label>
  -        </div>
  -      </div>
  -      <div class="mdl-cell mdl-cell--3-col">
  -        <div class="mdl-textfield mdl-js-textfield">
  -          <input class="mdl-textfield__input" type="text" #username4 id="username4">
  -          <label class="mdl-textfield__label" for="username4">Yet another (optional) username</label>
  -        </div>
  -      </div>
  -    </div>
  -
  -    <div class="mdl-grid">
  -      <div class="mdl-cell mdl-call--12-col">
  -        <button
  -              class="mdl-button mdl-js-button mdl-button--raised mdl-js-ripple-effect"
  -              (click)="fetchMovies([username1.value, username2.value, username3.value, username4.value])">
  -            Find movies
  -        </button>
  -      </div>
  -    </div>
  -
  -    <div class="mdl-grid">
  -      <div class="mdl-cell mdl-call--12-col">
           <ol>
             <li *ngFor="#movie of movies">
               {{ movie }}
  
positive.code: ''')
  class AppComponent {
    Iterable<Movie> movies = [];
  
    fetchMovies(List<String> users) {
      var client = new TraktWebService();
  
negative.code: 
      driver(client, users, process);
    }
  
    addUser(userName) {
      users = []..addAll(users)..add(userName.value);
      userName.value = "";
      if( users.length > 1 ) {
        fetchMovies(users);
      }
    }
  }
  