Testing a private method with access modifier in Scalatest

Question

I have the following issue.

Suppose I have the following class (example from here: Link ):

package com.example.people

class Person(val age: Int)

object Person {
  private def transform(p: Person): Person = new Person(p.age + 1)
}

So I have a package, and inside it I have a class with a private method.

Now I know using scalatest I can do something like this. In my test folder I have:

import org.scalatest.{ FlatSpec, PrivateMethodTester }

class PersonTest extends AnyFunSuite with PrivateMethodTester {

  test("A Person" should "transform correctly") {
      val p1 = new Person(1)
      val transform = PrivateMethod[Person]('transform)
      assert(p2 === p1 invokePrivate transform(p1))
    }
  }

Now, my question is, if I add an access modifier to my private method as follows (similar to the answer in this Link):

package com.example.people

class Person(val age: Int)

object Person {
  private[example] def transform(p: Person): Person = new Person(p.age + 1)
}

The test complains that transform is no longer a private method.

Is there a way I can still use the private method tester, even if I have an access modifier for a private function?

Answer 1

Given

package com.example.people

class Person(val age: Int)

object Person {
  private[example] def transform(p: Person): Person = new Person(p.age + 1)
}

you just have to make sure that corresponding test is also within example package

package example

class PersonTest extends AnyFunSuite {
  test("A Person should transform correctly") {
    val p1 = new Person(1)
    Person.transform(p1)    // transform is now accessible
    ...
    }
  }
}

in which case there is no need for PrivateMethodTester because private[example] makes the method available to all the members of example package.