Example.scala

class Example(serviceA: ServiceA, serviceB: ServiceB, serviceC: ServiceC) {
  def sum(x: Int, y: Int): Int = {
    serviceA.foo(x)
    serviceB.bar(y)
    // Doesn't call serviceC, so any test expecting it should fail
    x + y
  }
}

trait ServiceA {
  def foo(x: Int): Unit
}

trait ServiceB {
  def bar(y: Int): Unit
}

trait ServiceC {
  def baz(z: Int): String
}