Add ability to capture arguments

[vakhtang]

As far as I can tell ScalaMock lacks the ability to capture arguments a la Mockito's ArgumentCaptor. This StackOverflow post alludes to a mechanism that exists under-the-hood. It'd be great to expose it, or if it doesn't actually exist, add it. I imagine this can be implemented as a custom matcher.

[barkhorn]

See http://scalamock.org/user-guide/advanced_topics/ , topic "Returning values (onCall)"
In your onCall function, just save the value you're interested in into some field you defined above - done.

It's neither internal or undocumented :)

[vakhtang]

I'm aware of that, and was looking for something a bit more first-class, but ok!

[barkhorn]

i don't know what "more first-class" means. looking for some syntactic sugar?

[vakhtang]

Yes, more sugar. Perhaps something like this:

trait Foo {
  def increment(a: Int): Int
}

val fooMock = mock[Foo]
val captor = capture[Int]

(foo.increment _).expects(captor).once()

println(captor.value)

If there's an appetite for this I can take a stab at it.

[barkhorn]

got something on a branch that works like this:

  it should "capture the arguments of mocks - capture one" in {
    val m = mock[TestTrait]
    val c1 = CaptureOne[Int]()

    m.oneParam _ expects capture(c1) once()
    m.oneParam(42)
    c1.value should be (42)
  }

  it should "capture the arguments of mocks - capture all" in {
    val m = mock[TestTrait]
    val c = CaptureAll[Int]()

    m.oneParam _ expects capture(c) repeat 3
    m.oneParam(99)
    m.oneParam(17)
    m.oneParam(583)
    c.value should be (583)
    c.values should be (Seq(99, 17, 583))
  }

I'll push it later and you can review / comment @vakhtang ?

[vakhtang]

Looks great, thanks!