如何使用ScalaMock模拟call-by-name参数（如getOrElse）？

Question

我希望能够模拟getOrElse方法的返回值，以便它返回与ScalaMock一起传递的orElse call-by-name参数

trait ToBeMocked {
  def getOrElse(arg: Int)(orElse: => String): String
}

由于currying，必须使用ScalaMock。运行这个：

class CallByNameMockSpec extends Specification with MockFactory {

  trait ToBeMocked {
    def getOrElse(arg: Int)(orElse: => String): String
  }

  "Mocking functions with call-by-name arguments" should {
    "work" in {
      val m = mock[ToBeMocked]

      (m.getOrElse (_: Int)(_: String)).expects(101, *).onCall((x, y) => y)

      m.getOrElse(101)("result") must beEqualTo("result")
    }
  }

}

抛出异常：

[error]     ClassCastException:        
test.service.CallByNameMockSpec$$anonfun$1$$anonfun$apply$1$$anonfun$apply$3$$anonfun$apply$4 cannot be cast to java.lang.String (CallByNameMockSpec.scala:16)

Answer 1

诀窍是使用Product版本的onCall方法，将第二个参数转换为() => String并调用它：

class CallByNameMockSpec extends Specification with MockFactory {

  trait ToBeMocked {
    def getOrElse(arg: Int)(orElse: => String): String
  }

  "Mocking functions with call-by-name arguments" should {
    "work" in {
      val m = mock[ToBeMocked]

      (m.getOrElse (_: Int)(_: String)).expects(101, *).onCall(_.productElement(1).asInstanceOf[() => String]())

      m.getOrElse(101)("result") must beEqualTo("result")
    }
  }

}