CoroutineTestRule.kt

class CoroutineTestRule : TestRule,  
                          TestPolymorphicCoroutineScope by TestPolymorphicCoroutineScope() { 

  val dispatcher = coroutineContext[ContinuationInterceptor] as TestCoroutineDispatcher  
    
  override fun apply(  
    base: Statement, description: Description?  
  ) = object : Statement() {  
    override fun evaluate() {  
      @Throws(Throwable::class)  
      override fun evaluate() {  
        Dispatchers.setMain(dispatcher)  
  
        base.evaluate()  
  
        cleanupTestCoroutines()
        Dispatchers.resetMain()  
      }  
    }  
  }  
}