akauppi akauppi - 1 year ago 52
Scala Question

How to use ScalaTest "contain allOf" on two lists?

I was looking for a ScalaTest matcher to check that a list contains all of the needed elements (given within another list), but that may also be others.

contain allOf
demands to get two fixed elements, for some reason, the rest as varargs.

I can do a workaround like this, but it's tremendously ugly:

val list = List(1,2,3,4)
val wanted = List(1,2,3)
list should contain allOf ( wanted.head, wanted.tail.head, wanted.tail.tail :_* ) // ugly workaround

For giving a list as the match, there is
contain theSameElementsAs
. However, it does not allow extraneous elements to be in the probed value (I think).


  • am I missing something?

  • why is
    declared in the way that it must be given two fixed elements in the front (i.e. why not just pass varargs?)

  • should there be
    method (presumably with a better name)?

Some code I tried with:

val list = List.empty[String]
//list should contain allOf("a") // does not compile
list should contain allOf("a","b")
list should contain allOf("a","b","c")

val wanted = List("a","b","c")
//list should contain allOf( wanted ) // does not compile
list should contain allOf( wanted.head, wanted.tail ) // compiles, but tests the wrong thing; against List(head,List(tail))


Scala 2.11.4, ScalaTest 2.2.1


I probably end up using something like:

wanted.foreach( list should contain(_) )

However, this does not seem as readable to me (the
is kind of embedded) as the built-in collection constructs.

Answer Source

Bill Venners had this to say on the ScalaTest mailing list:

Yes, we didn't want to hold up the 2.0 release to add that, but have since added it. I believe we added it to master, though, not the 2.2.x branch. Regardless, the syntax looks like:

xSet should contain allElementsOf (ySet)

Link to the message.