Scala Testing with Mock objects within objects - scala

Question

While Testing Called1.writeData and mocking using the traits, control is still going to the original implementation. Need help from experts.
object Caller1() {
def method1(param1:String, param2:Long) {
val param3=param1 //Some transformation
val param4=param2
Called1.writeData(param3, param4)
}
}
object Called1 extends Called1Trait {
val producer = Called2.createProducer
def writeData {
val data = createData(param1)
Called2.MethodA(...)
}
def createData(param1) {
// Some code
}
}
object Called2 extends Called2Trait {
def createProducer {
// Some code
}
def methodA {
// Some code
}
def methodB {
// methodA is used here
}
}
I have used mocking of the traits and using when and then to bypass the execution. Yet it is going to the methods. I have used any().
val CalledObject1Mock = mock[CalledObject1Trait]
val CalledObject2Mock = mock[CalledObject2Trait]
when(CalledObject1Mock.createProducer).thenReturn(ProducerMock)
when(CalledObject1Mock.writeData(any(),any())).thenReturn(true)
when(CalledObject1Mock.createData(any())).thenReturn(MockedData)
when(CalledObject2Mock.methodA(any(), any(), any())).thenReturn(true)
when(CalledObject2Mock.methodB(any(), any(), any())).thenReturn(true)
Called1.writeData(testParam1, testParam2) // this is failing
We have used scala Mockito. So do not intend to use any other framework.
import org.scalatest.funsuite.AnyFunSuite
import org.scalatest.BeforeAndAfterAll
import org.scalatest.flatspec.AnyFlatSpec
import org.scalatestplus.mockito.MockitoSugar
import org.scalatest.matchers.should._
trait BaseTestSuite extends AnyFunSuite with BeforeAndAfterAll with Matchers with MockitoSugar {

Answer 1

The current design does not allow to test it by Mock.
You mocked the called objects but don't use them. The original Called1 does not know about mocked objects.
You should not mock a class under the testing.
To fix it I would suggest redesigning your classes this way:
class Caller1(called1: Called1Trait) {
def method1(param1:String, param2:Long) {
val param3=param1 //Some transformation
val param4=param2
called1.writeData(param3, param4)
}
}
class Called1(called2: Called2Trait) extends Called1Trait {
val producer = called2.createProducer
def writeData {
val data = createData(param1)
called2.methodA(...)
}
def createData(param1) {
// Some code
}
}
class Called2 extends Called2Trait {
def createProducer {
// Some code
}
def methodA {
// Some code
}
def methodB {
// methodA is used here
}
}
So, assume you want to test the Called1. The test will look like this:
val called2Mock = mock[Called2Trait]
when(called2Mock.methodA(any(), any(), any())).thenReturn(true)
when(called2Mock.methodB(any(), any(), any())).thenReturn(true)
val called1 = new Called1(called2Mock)
called1.writeData(testParam1, testParam2)
Now the called1 knows that called2 is mocked object and will call the mocked methodA().