Unable to stub a Class with overloaded constructors - Scalamock

Question

I am trying to stub a class called 'Producer' with the following signature:

class Producer[K, V](private val underlying : kafka.producer.Producer[K, V]) extends scala.AnyRef {
  def this(config : kafka.producer.ProducerConfig) = { /* compiled code */ }
  def send(message : kafka.producer.KeyedMessage[K, V]) : scala.Unit = { /* compiled code */ }
  def send(messages : java.util.List[kafka.producer.KeyedMessage[K, V]]) : scala.Unit = { /* compiled code */ }
  def close : scala.Unit = { /* compiled code */ }
}

the code val fakeProducer = stub[Producer[String, String]]

Following is the error:

I have been stuck with this issue for sometime now. Is there a way we can create this stub object? Any help would be appreciated.

Best Regards.

Answer 1

Not an exact answer as I don't have an IDE right now, and not sure which version of scalamock, kafka, scala you use but hopefully this gives you an idea that works.

I would subclass your type to mock and be explicit which constructor the subclass refers to.

class MockableProducer extends kafka.javaapi.producer.Producer[String, String](null.asInstanceOf[kafka.producer.Producer[String,String])
val producer = stub[MockableProducer]

Be aware that all sideeffects of the Producer class will still run when the stub is created, which can give some unexpected NPEs