Why does Mockito verifyNoMoreInteractions has problem with Scala default values - scala

Question

For a mocked class I have a method for which I would like to test whether there are no more interactions then needed, which looks similar to:
def someMethod(someMandatoryParam: Int, canBeDefaultIds: Option[Ids] = None): Future[Failures] = {...}
when I am mocking to invoke this method without the default parameter and I verify it that way:
verify(someClass).someMethod(someInt)
and then check if there was no more interactions:
verifyNoMoreInteractions(someClass)
I am getting an error that here was some unexpected interactions.
But when in implementation I change this method to use None instead of default value and verify:
verify(someClass).someMethod(someInt, None)
verifyNoMoreInteractions(someClass)
It works correctly.
Is there a problem with Mocikto and default values in Scala?

Answer 1

Default arguments is Scala specific feature which Java Mockito is likely not aware of. Consider how Scala code looks after -Xprint:jvm phase
abstract trait SomeClass extends Object {
def someInt(a: Option): Option = a;
<synthetic> def someInt$default$1(): Option = scala.None;
}
Notice how the default argument became just another method someInt$default$1. Try using mockito-scala which is designed with Scala in mind, for example the following test passes
import org.mockito.{ArgumentMatchersSugar, IdiomaticMockito}
import org.scalatest.flatspec.AnyFlatSpec
import org.scalatest.matchers.should.Matchers
trait SomeClass {
def someInt(a: Option[Int] = None) = a
}
class MockitoScalaDefaultArgsSpec extends AnyFlatSpec with Matchers with IdiomaticMockito with ArgumentMatchersSugar {
"mockito-scala" should "handle default arguments" in {
val someClass = mock[SomeClass]
someClass.someInt()
someClass.someInt() was called
someClass wasNever calledAgain
}
}