title: xUnit v2 IUseFixture<> replacement
body: <p>I'm trying to upgrade to xUnit 2 beta (mostly because of better test discovery) but stumbled over <code>IUseFixture&lt;&gt;</code>:</p>
  
  <pre><code>public abstract class TestCaseBase : IUseFixture&lt;SelfHostFixture&gt; 
  { /*common stuff here*/ }
  
  public class Controller1Test : TestCaseBase {}
  
  public class Controller2Test : TestCaseBase {}
  </code></pre>
  
  <p>I found that new <code>IClassFixture&lt;&gt;</code> was almost what I needed except the fixture was created/disposed for every descendant classes (<code>Controller1Test</code>, <code>Controller2Test</code>) instead of just once. Well, I could move <code>IClassFixture&lt;SelfHostFixture&gt;</code> declaration to every test class from the base but why would I setup/dispose my server multiple times? <code>ICollectionFixture&lt;&gt;</code> didn't worked for me (the fixture's ctor was never fired).</p>
  
  <p>Basically, what I want is:</p>
  
  <ol>
  <li>"Per run" fixture (must be instantiated only once per tests run)</li>
  <li>Enable parallel runs because my tests are just stateless HTTP calls (I think <code>ICollectionFixture&lt;&gt;</code> won't work at all because tests within same collection cannot be run in parallel, right?)</li>
  </ol>
  
  <p>What am I missing?</p>