How to do an instanceof check with Scala(Test)

Scala is not Java. Scala just does not have the operator instanceof instead it has a parametric method called isInstanceOf[Type].

You might also enjoy watching a ScalaTest Crash Course.

With Scalatest 2.2.x (maybe even earlier) you can use:

anInstance mustBe a[SomeClass]

If you want to be less JUnit-esque and if you want to use ScalaTest's matchers, you can write your own property matcher that matches for type (bar type erasure).

I found this thread to be quite useful: http://groups.google.com/group/scalatest-users/browse_thread/thread/52b75133a5c70786/1440504527566dea?#1440504527566dea

You can then write assertions like:

house.door should be (anInstanceOf[WoodenDoor])

instead of

assert(house.door instanceof WoodenDoor)

The current answers about isInstanceOf[Type] and junit advice are good but I want to add one thing (for people who got to this page in a non-junit-related capacity). In many cases scala pattern matching will suit your needs. I would recommend it in those cases because it gives you the typecasting for free and leaves less room for error.

Example:

OuterType foo = blah
foo match {
  case subFoo : SubType => {
    subFoo.thingSubTypeDoes // no need to cast, use match variable
  }
  case subFoo => {
    // fallthrough code
  }
}