override methods for test

overrideMethodForMock.scala

  it should "something dirty" in {
    val list: java.util.List[String]= new java.util.ArrayList[String] {
      @throws(classOf[NullPointerException])
      override def get(a: Int): String = {
        throw new NullPointerException()
      }
    }

    a[NullPointerException] should be thrownBy { // Result type: Assertion
      list.get(0)
    }
  }