如何使用ScalaMock模拟按名称调用参数(如getOrElse)?

问题描述

我希望能够模拟getOrElse方法的返回值，以便它返回通过ScalaMock作为orElse调用名称参数传递的内容

I'd like to be able to mock a return value of getOrElse method so that it returns what is passed as orElse call-by-name argument with ScalaMock

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

必须使用ScalaMock，因为它会引起混乱.运行此:

ScalaMock has to be used because of currying. Running this:

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")
    }
  }

}

引发异常:

[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)

推荐答案

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

The trick is to use Product version of onCall method, convert the second argument to () => String and call it:

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")
    }
  }

}

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