如何模拟Scala单例对象？

Question

我试图模拟Scala单例对象.特别是,我需要模拟play.api.libs.ws.WS服务组件(被测试的类)中使用的对象.使用Mockito这是不可能的,测试执行失败的方式如下:

[error]    MockitoException: : 
[error] Cannot mock/spy class play.api.libs.ws.WS$
[error] Mockito cannot mock/spy following:
[error]   - final classes
[error]   - anonymous classes
[error]   - primitive types  (GeolocationSpec.scala:18)

在这里阅读,似乎Scalamock允许这样做:

要模拟独立的单例对象,请使用 org.scalamock.annotation.mockObject.

我的服务组件是这样的:

trait GeolocationService {
  def wsClient = WS
  def getPath(origin: Location, destination: Location): Future[Route]
}

class DefaultGeolocationService extends GeolocationService {

  val serviceProviderEndpoint = Play.current.configuration.getString("api.directions.endpoint")

  override def getPath(origin: Location, destination: Location): Future[Route] = {

    val params = Seq(
      "origin" -> s"${origin.lat},${origin.lon}",
      "destination" -> s"${destination.lat},${destination.lon}"
    );
    val resp = wsClient.url(serviceProviderEndpoint.get).withQueryString(params: _*).get()
    resp.map {
      // omitted code
    }
  }
}

我的build.sbt具有所有这些依赖项:

[...]
"org.scalatest" %% "scalatest" % "2.2.1",
"org.specs2" %% "specs2" % "2.3.13" % "test",
"org.scalamock" %% "scalamock-specs2-support" % "3.0.1" % "test",
"org.scalamock" %% "scalamock-scalatest-support" % "3.0.1" % "test",
"org.scalamock" %% "scalamock" % "3.0.1",
[...]

但我找不到这个: org.scalamock.annotation.mockObject

也许这也可以使用EasyMock和PowerMock完成,但我找不到任何Scala示例代码.

任何的想法？

Answer 1

使用ScalaMock 3模拟单例对象是不可能的,但Paul Butcher希望在ScalaMock 4中重新引入此功能(请参阅http://paulbutcher.com/2014/04/15/scalamock-status-report/)

Answer 2

为什么不使用蛋糕图案？

它有点冗长，但它会解决你的模拟问题。

trait GeolocationServiceComponent {
   val geolocationService:GeolocationService
   trait GeolocationService {      
      def wsClient
      def getPath(origin:Location, destination: Location): Future[Route]   
   }
}

trait GeolocationServiceComponentImpl {
   val geolocationService = new GeolocationService {
      override def wsClient = WS
   }
}


class DefaultGeolocationService extends GeolocationServiceComponent ...

//Defined into your test class
trait MockGeolocationServiceComponent {
       val geolocationService = Mock[GeolocationService]
//Here you define your mock logic       
}

你也可以使用 monad 来做到这一点，但我从未实现过，它的描述如下： Scala 依赖注入：隐式参数的替代方案