Mocking Scala void function using Mockito

Question

I found a few answers for this but nothing is working for me.

Trying to mock Apache Shiro Subject interface login method which returns void.

Interface:

    void login(AuthenticationToken token) throws AuthenticationException;

I have tried :

   #1
  val subject = mock[Subject]
  doNothing().when(subject).login(new UsernamePasswordToken())

   #2
  val subject = mock[Subject]
  doNothing().when(subject).login(any[UsernamePasswordToken])

   #3
  when(subject.login(any[UsernamePasswordToken])).thenAnswer(new Answer[Void]() {
      override def answer(invocation: InvocationOnMock): Void = {
       null:Void
      }

I keep getting NullPointerException on login. My goal is test around the login method and test some success cases along with some failure cases where this method throws an exception.

Coruscate

The default behavior in Mockito is to return nothing if you don't "stub" a particular method. That is, have you tried removing the whole `doDonthing()..." line? – Annates

Yea so I did read something similar but leaving that line as mock(subject) was giving me NPE – Coruscate

Consider the () as [] typing on my phone – Coruscate

can you reproduce this into a short project? I am pretty sure Mockito is stubbing all methods by default. It shouldn't raise a NPE. – Annates

Will do will also go back and I can post more code from method under test and test exception perhaps I read it wrong – Coruscate

So you were correct mock[Subject] should have been fine because Mockito is stubbing all methods by default. The issue was higher up with how this projects test framework/utility classes were setup. The subject I was mocking was not the one fed to the request. So the code was using a different instantiated subject which is why it was going into actual implementation. – Coruscate

Answer 1

The default behavior in Mockito is to return nothing if you don't "stub" a particular method. No need to force a void() function to doNothing() since it's doing nothing by default.

Annates