title: Gradle not running TestNG tests, even with test.useTestNG()
body: <p>My <code>build.gradle</code> looks like this:</p>
  
  <pre><code>apply plugin: 'scala'
  apply plugin: 'java'
  
  sourceCompatibility = 1.8
  version = '1.0'
  
  repositories {
      mavenCentral()
  }
  
  dependencies {
      compile "org.scala-lang:scala-library:2.11.4"
  
      compile 'org.reactivestreams:reactive-streams:1.0.0.RC1'
      compile 'org.reactivestreams:reactive-streams-tck:1.0.0.RC1'
  
      testCompile group: 'junit', name: 'junit', version: '4.11'
      testCompile group: 'org.testng', name: 'testng', version: '5.14.10'
  }
  
  test {
      useTestNG()
  }
  </code></pre>
  
  <p>I have some implementation in Scala, and TestNG test in java. The test class actually does not contain any tests, but it's parent class does. Gradle seems to think there are no tests in the class.</p>
  
  <pre><code>Skipping task ':testClasses' as it has no actions.
  :testClasses UP-TO-DATE
  :testClasses (Thread[main,5,main]) completed. Took 0.001 secs.
  :test (Thread[main,5,main]) started.
  :test
  Skipping task ':test' as it is up-to-date (took 0.048 secs).
  :test UP-TO-DATE
  </code></pre>
  
  <p>The test class is compiled in <code>build/classes/test</code></p>