title: The built-in library 'dart:html' is not available on the stand-alone VM
body: <p>I'd like to be able to unit test my custom polymer elements. </p>
  
  <p>Given a component in lib/web_components:</p>
  
  <pre><code>class Foo extends PolymerElement {
    Foo.created() : super.created();
  }
  </code></pre>
  
  <p>and a test in test/web_components:</p>
  
  <pre><code>main() {
    test("Should Be a PolymerElement", (){
      Foo undertest = new Foo.created();
  
      expect(undertest, new isInstanceOf&lt;PolymerElement&gt;());
    });
  }
  </code></pre>
  
  <p>Running the test results in the error mentioned in the title. How can I avoid this error? </p>
  
  <p>Edit:</p>
  
  <p>So I've tried adding <code>@TestOn('content-shell')</code> at the top of my client side test files, and adding <code>@TestOn('vm')</code> to the server side tests. </p>
  
  <p>In Grinder I have:</p>
  
  <pre><code>@Task('Test')
  test() {
    new PubApp.local('test').run([]);
    new PubApp.local('test').run(["-p", "content-shell"]);
  }
  </code></pre>
  
  <p>The server-side tests run fine but the client-side tests throw the following error:</p>
  
  <pre><code>pub run test -p content-shell test/web_component/foo_test.dart
    "Failed to start content shell: No such file or directory"
  </code></pre>
  
  <p>Edit 2:</p>
  
  <p>I've tried running in the dartium platform with the following command since content-shell doesn't seem to work:</p>
  
  <pre><code>pub run test:test -p dartium test/web_component/foo_test.dart
  </code></pre>
  
  <p>The result is:</p>
  
  <pre><code>Failed to load "test/web_component/foo_test.dart": type 'test.backend.declarer.Declarer' is not a subtype of type 'test.backend.declarer.Declarer' of 'function result'.
    packages/test/test.dart 44:32                          _declarer
    packages/test/test.dart 108:5                          test
    foo_test.dart 9:3                     main
    package:test                                           IframeListener.start
    foo_test.dart.browser_test.dart 6:18  main
  </code></pre>