title: The @Rule > must be public ValidationError in Kotlin Junit test
body: <p>I tried to use a unit test rule annotation and Android Studio didn't highlight any error here:</p>
  
  <pre><code>@Rule val htmlManager = HtmlManager()
  </code></pre>
  
  <p>However after executing the test following error happens:    </p>
  
  <blockquote>
    <p>org.junit.internal.runners.rules.ValidationError: The @Rule
    'htmlManager' must be public.</p>
  </blockquote>
  
  <p>How to fix this?</p>