使用PrivateMethodTester测试采用通用类型的私有方法

Question

如何在Scala中使用privateMethodTester测试采用通用类型的私有方法？

假设我有以下方法：

private def parseValueForJsonKeyWithReturnType[A: TypeTag](
   node: JsonNode, 
   key: String, 
   defaultValue: Option[A] = None): A = {

    val parsedValue = Option(node.get(key)).map(value => { 
      typeOf[A] match {
         case t if t =:= typeOf[String] =>
           value.textValue()
         case t if t =:= typeOf[Double] =>
           value.asDouble()
         case t if t =:= typeOf[Long] =>
           value.asLong()
         case _ => throw new RuntimeException(s"Doesn't support conversion to [type=${typeOf[A]}] for [key=${key}]")
       }
    })

    parsedValue.getOrElse(defaultValue.get).asInstanceOf[A]
  }

我可以这样调用方法

parseValueForJsonKeyWithReturnType[Boolean](jsonNode, key="hours")
parseValueForJsonKeyWithReturnType[String](jsonNode, key="hours")
parseValueForJsonKeyWithReturnType[Long](jsonNode, key="hours")

在测试中，我正在尝试

val parseValueForJsonKeyWithReturnTypeInt = PrivateMethod[Int]('parseValueForJsonKeyWithReturnType)
a[RuntimeException] shouldBe thrownBy (object invokePrivate parseValueForJsonKeyWithReturnType[Int](jsonNode, "total" , None))

以确保它将为不受支持的类型抛出运行时异常

但是我得到这个错误：

error: value parseValueForJsonKeyWithReturnType of type SerializerTest.this.PrivateMethod[Int] does not take type parameters.

如果我尝试不使用类型参数，则构建可以成功，但是会出现非法ArgumentException

Expected exception java.lang.RuntimeException to be thrown, but java.lang.IllegalArgumentException was thrown. 

Cause: java.lang.IllegalArgumentException: Can't find a private method named: parseValueForJsonKeyWithReturnType

我在做什么错？语法可能错误。