The mock of my class isn't getting called - scala

Question

I have a HelperMethod class.
class HelperMethods {
def getUniqueID(): UUID = {
UUID.randomUUID()
}
def bucketIDFromEmail(email:String): Int = {
val bucketID= email(0).toInt
println("returning id "+bucketID+" for name "+email)
bucketID
}
}
And an object which has an instance of HelperMethods
package object utilities{
private val helper = new HelperMethods()
def getUniqueID(): UUID = helper.getUniqueID()
def bucketIDFromEmail(email:String): Int = helper.bucketIDFromEmail(email)
}
I wrote a spec to test that my mock works correctly.
class UserControllerUnitSpec extends PlaySpec {
val mockHelperMethods = mock(classOf[HelperMethods])
when(mockHelperMethods.getUniqueID()).thenReturn(UUID.fromString("87ea52b7-0a70-438f-81ff-b69ab9e57210"))
when(mockHelperMethods.bucketIDFromEmail(ArgumentMatchers.any[String])).thenReturn(1)
"mocking helper class " should {
"work" in {
val bucketId = utilities.bucketIDFromEmail("t#t.com")
println("user keys are " + userKeys)
val id: UUID = utilities.getUniqueID()
println("got id " + userKeys)
bucketId mustBe 1
id mustBe UUID.fromString("87ea52b7-0a70-438f-81ff-b69ab9e57210")
}
}
}
the test fails with reason 116 was not equal to 1. This corresponds to line
bucketId mustBe 1 in the spec. I can see the print returning id 116 for name t#t.com. I shouldn't see it as I am trying to mock this class. I suspect that it could be because the utilities object is getting created before the statement val mockHelperMethods = mock(classOf[HelperMethods]) in the spec.
Question 2- Is there a way to mock HelperMethods and make utilities use the mocked class?

Answer 1

You have mocked HelperMethods but not utilities.
Question 2- Is there a way to mock HelperMethods and make utilities use the mocked class?
It is not possible to mock an object.
If you want, you have to extract the behavior in a trait.
Here is a solution that would work:
package utils
// move the behavior to a trait:
trait UtitilitiesTrait {
private[utils] def helper = new HelperMethods()
def getUniqueID(): UUID = helper.getUniqueID()
def bucketIDFromEmail(email: String): Int = helper.bucketIDFromEmail(email)
}
// provide an object for real use
object Utilities extends UtitilitiesTrait
// override helper for test mock
object TestUtilities extends UtitilitiesTrait {
private[utils] override def helper = mock(classOf[HelperMethods])
}
And here is your test:
class UserControllerUnitSpec extends PlaySpec {
val mockHelperMethods = mock(classOf[HelperMethods])
object TestUtilities extends UtitilitiesTrait {
private[utils] override def helper = mockHelperMethods
}
when(mockHelperMethods.getUniqueID()).thenReturn(UUID.fromString("87ea52b7-0a70-438f-81ff-b69ab9e57210"))
when(mockHelperMethods.bucketIDFromEmail(ArgumentMatchers.any[String])).thenReturn(1)
"mocking helper class " should {
"work" in {
val bucketId = TestUtilities.bucketIDFromEmail("t#t.com")
println("user keys are " + userKeys)
val id: UUID = TestUtilities.getUniqueID()
println("got id " + userKeys)
bucketId mustBe 1
id mustBe UUID.fromString("87ea52b7-0a70-438f-81ff-b69ab9e57210")
}
}
}

Answer 2

The typical pattern that enables mocking objects used internally is to inject them, or at least provide a way to inject an alternate.
Since Utilities is an object, you can't inject using a constructor. You could still introduce a setter method.
If you'd like to discourage use of the setter for anything other than unit tests, make it package-private, and you might also prefix the name with "qa":
private[utils] def qaSetHelperMethods(qaHelper: HelperMethods): Unit