title: Sling Mock is not allowing to get ResourceResolverFactory
body: <p>Given code:</p>
  
  <pre><code>public class TestExample {
    @Rule
    SlingContext slingContext = new SlingContext(ResourceResolverType.JCR_MOCK);
  
  
    @Test
    public void test() {
      ResourceResolverFactory rrf = slingContext.getService(ResourceResolverFactory.class);
    }
  }
  </code></pre>
  
  <p>Gives me:</p>
  
  <pre><code>org.apache.sling.resourceresolver.impl.ResourceResolverFactoryActivator$1 cannot be cast to org.apache.sling.api.resource.ResourceResolverFactory
  java.lang.ClassCastException
      at example(ExampleTest.java:21)
  </code></pre>
  
  <p>Do I have to use <code>slingContext.resourceResolver()</code> method? It is not flexible as I want, because of existing only <code>ResourceResolver</code> instance at once (and it is closed on <code>tearDown</code> which my class is doing by itself). Can I avoid this problem somehow?</p>