Mock classes with traits

Is there any library that provides tools for mocking classes with traits (both can be statefull)?

Simplified example:

trait T {
  var xx: List[Int] = List[Int]()
  def t(x: Int) {
    xx ::= x    //开发者_运维问答throws NPE, xx == null, even after implicit initialization
  }
}

class A extends T {
}

class Testable(a: A) {
  def bar() {
    a.t(2)
  }
}

@Test def testFoo() {
  val a: A = mock[A]
  val testable = new Testable(a)
  testable.bar()
  verify(a).t(2)
}

Paul Butcher has been working on Borachio, a Scala mocking library. It supports mocking of traits, classes, functions and objects. See the following blogs for more information:

http://www.paulbutcher.com/2011/02/announcing-borachio-native-scala-mocking/ http://www.paulbutcher.com/2011/07/power-mocking-in-scala-with-borachio/

Well ... I don't have an answer, but I think I can offer a hint at where the problem is coming from. I took a look at A.class and found this (de.schauderhaft.testen is the package I used):

  // Method descriptor #21 (I)V
  // Stack: 2, Locals: 2
  public bridge void t(int x);
    0  aload_0 [this]
    1  iload_1 [x]
    2  invokestatic de.schauderhaft.testen.T$class.t(de.schauderhaft.testen.T, int) : void [26]
    5  return
      Line numbers:
        [pc: 0, line: 13]
      Local variable table:
        [pc: 0, pc: 6] local: this index: 0 type: de.schauderhaft.testen.A
        [pc: 0, pc: 6] local: x index: 1 type: int 

I'm no byte code expert but this

2  invokestatic de.schauderhaft.testen.T$class.t(de.schauderhaft.testen.T, int) : void [26]

looks like the call to t(Int) is actually a called to a static method and you can't mock static methods. PowerMock would help, but probably ugly to use.

I just released ScalaMock 2.0. As well as functions and interfaces, ScalaMock can mock:

• Classes
• Singleton and companion objects (static methods)
• Object creation (constructor invocation)
• Classes with private constructors
• Final classes and classes with final methods
• Operators (methods with symbolic names)
• Overloaded methods