ArgumentMatcher for Kotlin

Question

I'm trying to use ArgumentMatcher in my tests. I do next:

Mockito.`when`(someRepository.save(
        argThat { it.name == someName } // Here I want to do mock for all objects with name someName
    )).thenReturn(save(someEntity))

And I get next error: Type inference failed: Not enough information to infer parameter T in fun when(p0: T!): OngoingStubbing!

How properly write ArgumentMatcher in Kotlin?

Answer 1

I found a solution by adding ArgumentMatcher from java class. My IDE converted it to Kotlin:

In java:

Mockito.when(someRepository.save(ArgumentMatchers.argThat(entity-> entity.getName().equals("someName")
            && entity.getDescription().equals("somedescritpion")
            ))));

In Kotlin:

Mockito.`when`<Any>(someRepository.save(ArgumentMatchers.argThat { (name, _, description, ) ->
        (name == "someName" && description == "somedescritpion"
                )
    }))

Note: You should add _ if you have some fields which you don't want to consider in the matcher.

Answer 2

I strongly recommend using nhaarman's mockito-kotlin instead of vanilla Mockito. It has numerous advantages that allow it to be used with fewer issues in Kotlin as Mockito is designed for use in Java. You can see this guide for how to use argument matchers in Kotlin. Your example will look very similar, but should have less issues with type inference.

Answer 3

Use the someRepository.save(Mockito.any<String>()) . That would not care about what argument you are passing as long as it is a String. Empty values count too.