TestPolymorphicCoroutineScope.kt

@ExperimentalCoroutinesApi  
interface TestPolymorphicCoroutineScope : TestCoroutineScope,  
  DefaultCoroutineScope,  
  IOCoroutineScope,  
  MainCoroutineScope,  
  MainImmediateCoroutineScope,  
  UnconfinedCoroutineScope
  
@ExperimentalCoroutinesApi  
private class TestPolymorphicCoroutineScopeImpl(
  context: CoroutineContext = EmptyCoroutineContext  
) : TestPolymorphicCoroutineScope,
  // delegates all functionality to TestCoroutineScope
  // uses the TestCoroutineScope factory function
  // to inject the TestCoroutineDispatcher and TestCoroutineExceptionHandler into the context
  TestCoroutineScope by TestCoroutineScope(context)  
  
@ExperimentalCoroutinesApi  
fun TestPolymorphicCoroutineScope(
  context: CoroutineContext = EmptyCoroutineContext  
): TestPolymorphicCoroutineScope = TestPolymorphicCoroutineScopeImpl(
  context = context + dispatcher  
)