Mockito: Matcher Support for Kotlin

[ihanjo]

I've recently started using Kotlin and am loving it so far. I've however had to use some workarounds for Mockito matchers, since Kotlin doesn't like null -- a great thing IMO. See http://stackoverflow.com/q/30305217

There is a library out there called MockitoKotlin that provides matchers that do work with Kotlin, but I'd rather use Mockito directly since that way I can have access to the latest features and patches by official Mockito.

What do you guys think? Is this a reasonable ask? I know Kotlin isn't Java, but it is gaining popularity. :)

[TimvdLippe]

I think this usecase can be safely supported with the new lambda when syntax and implementation. Will try it out!

[ihanjo]

@TimvdLippe Do you think it's a lot of work to support it? What do you envision this snippet would look like with the lambda when syntax?

when(mockGreeter.welcome(eq("John"))).thenReturn("Welcome, John!");

[TimvdLippe]

@ihanjo There is an open proposal PR at #742 . The syntax I imagine will be

when(mockGreeter::welcome).invokedWith(eq("John")).thenReturn("Welcome, John!");

Note this is typesafe and Kotlin-friendly because passing the matcher is decoupled from the method invocation.

[bric3]

I'm not sure this should be part of mockito yet. As matchers will create new mocks for types without default values.