单元测试 – 模拟重载方法

At present,ScalaMock can only mock traits,Java interfaces,and non-final 
classes that define a default constructor

由于PrintStream类既不是接口也不是默认构造函数,我的猜测是scalamock无法正确模拟它,你看到的错误是其副作用.如果您更改了代码以使用OutputStream(这是一个接口,因此符合scalamock的限制),您可以像这样进行重载方法模拟：

val mockStream = mock[OutputStream]      
(mockStream.write(_:Int)) expects(1)
(mockStream.write(_:Array[Byte])) expects(Array[Byte](1,2,3))

就个人而言,我更喜欢M001在Specs2年内使用,因为它没有这些限制.使用PrintWriter的类的示例,然后使用Mockito模拟该类的测试规范如下：

import java.io.PrintStream
import java.io.File
import org.specs2.mutable.Specification
import org.specs2.mock.Mockito

class MockitoExample extends Specification with Mockito{
  val mockPrinter = mock[PrintStream]
  val myPrinter = new MyPrintingClass{
    override val printer = mockPrinter
  }

  "A request to print and attay of strings" should{
    "call println on the PrintStream for each string supplied" in {
      myPrinter print Array("foo","bar")
      there was one(mockPrinter).println("foo")
      there was one(mockPrinter).println("bar")
    }
  }
}

class MyPrintingClass{
  val printer = new PrintStream(new File("foo.txt"))

  def print(strings:Array[String]) = strings foreach (printer.println(_))
}

现在这只是一个非常简单的例子,只使用没有预测试截断的测试后验证(因为println具有Unit返回类型),但至少你可以看到Mockito没有受到与scalamock相同的限制.您可以阅读有关使用Mockito和Specs2 here的更多信息.