ArgCaptor results in NullPointerException when trying to access value

[michael-camacho]

My code is of the form:

val thingsCaptor = ArgCaptor[Seq[Thing]]
verify(someMock).doStuff(thingsCaptor)

When I try to access the value in any way, even by doing a toSeq, I get a NullPointerException. I know that something should be captured, since I can get a valid value if I use the standard Mockito ArgumentCaptor.forClass approach.

It's a shame, because I really like the new syntax. :)

[ultrasecreth]

So I just quickly tried

class Bar {
  def seqOfThings[T](v: Seq[T]): Int = ???
}

    "work with Seq[T]" in {
      val aMock  = mock[Bar]
      val captor = ArgCaptor[Seq[String]]

      aMock.seqOfThings(Seq("v1", "v2"))

      verify(aMock).seqOfThings(captor)

      captor.value shouldBe Seq("v1", "v2")
      captor hasCaptured Seq("v1", "v2")
    }

and it works, can you post a full code example? also, what version of the lib are you using?

[ultrasecreth]

@michael-camacho is this still an issue?

[ultrasecreth]

Can't reproduce, closing it

[michael-camacho]

@bbonanno My apologies! I've not been receiving notifications for some reason. I'll have to check my settings. I only even realised you'd responded as a consequence of manually checking the issue just now. :(

I was using version 1.0.2, but the issue is still present in 1.0.5.

I hadn't tried captor.value before, and indeed that does work and returns a Seq of values, but the problem I reported originally still stands -- doing captor.toSeq still throws a NullPointerException. The same thing happens if I try to leverage the implicit conversion to the captured type in other ways.

[ultrasecreth]

@michael-camacho Sorry but I don't understand the problem, where would you do captor.toSeq? could you post a full piece of code that I can copy and paste to reproduce the issue?

[michael-camacho]

@bbonanno Er, my understanding is that the new syntax supports an implicit conversion of the captor to the underlying type, so that you can use it in place of the actual value. Maybe I'm wrong though?

You would do captor.<reallyActuallyAnySeqMethod> anywhere after you'd captured the value. To modify your example, for instance:

class Bar {
  def seqOfThings[T](v: Seq[T]): Int = ???
}

"work with Seq[T]" in {
  val aMock  = mock[Bar]
  val captor = ArgCaptor[Seq[String]]

  aMock.seqOfThings(Seq("v1", "v2"))

  verify(aMock).seqOfThings(captor)

  captor.head shouldBe "v1"
}

In this version, captor.head should return the string value "v1", but instead it results in a NullPointerException.

[ultrasecreth]

@michael-camacho The implicit conversion is from captor to captor.capture
There is no conversion between captor and captor.value as there can be only one implicit conversion Captor[T] => T

That's why the captor provides a convenience matcher def hasCaptured(expectation: T) that enables writing captor hasCaptured Seq("v1", "v2")

[michael-camacho]

@bbonanno Ah, for the verify, I see! Gah, it seems obvious now. >_<

Thanks for taking the time to explain! I can see why the "problem" sounded so confusing now. I think Mockito's operation is still a bit too magical to me, and I have to spend more time looking at how it works below the surface. ;-)

[ultrasecreth]

@michael-camacho No problem, happy to help!