Add assertSameElements for collections

[danicheg]

Adding assertSameElements() for comparison elements of collections.
It also might be useful for comparison collections when == equality is not applicable (e.g. Array[A]).
For those collections possible to do plain assertion:

assert(Array() sameElements Array())

but this will lead to a poor error message.

[danicheg]

.toIterator here just for back compat with Scala 2.11.

[olafurpg]

Thank you for this contribution! I am personally on the fence about this addition since it's possible to achieve similar functionality with

• assertEquals(a.toSet b.toSet)
• assertEquals(a.sorted, b.sorted)

The benefit of those assertions is that they make it clearer whether you're ignoring only the ordering differences, or duplicate elements as well.

However, I'm not opposed to merging this feature if more people think it would be useful. My biggest reservation is that we'll end up with too many assertions. I want to try to keep the number of assertions small.

[olafurpg]

It would be good to refactor this test so that every individual assertion is a separate test

def checkFail(obtained, expected) = test(obtained.toString.fail) {
  assertSameElements(obtained, expected)
}

Currently, the test only asserts that at least a single statement in this body throws an exception.

[danicheg]

Good point. Make me known if that PR will have a chance to get merged, then I'll fix that.

[olafurpg]

Can you elaborate on "unpredictable result"?

[danicheg]

I mean that

val x = List("a" -> 1, "b" -> 2, "c" -> 3, "d" -> 3, "f" -> 4)
val y = Set("a" -> 1, "b" -> 2, "c" -> 3, "d" -> 3, "f" -> 4)
x sameElements y // false

and

val x = List("a" -> 1, "b" -> 2, "c" -> 3, "d" -> 3)
val y = Set("a" -> 1, "b" -> 2, "c" -> 3, "d" -> 3)
x sameElements y // true

a really unpredictable behaviour.

[danicheg]

@olafurpg I came to this assertion after the migration of a bunch of libs working with a network where it's common to check some Array[Byte]s. As for me, it's good to have this assertion to not convert Array to Seq and don't use assert on equals check. But I agree that it makes sense to don't procreate too many assertions, as we know, it always ends up badly :)

[olafurpg]

@danicheg Would it make sense to create a method assertArraySameElements instead? It sounds like this assertion is only relevant for arrays. MUnit already has custom assertions for Double/Float primitives.

[danicheg]

@olafurpg as for me, it's more flexible to have that assertion for Iterables, than only for Arrays. Another take is checking elements of sequences (or even Iterables) different types (though I don't endorse it).

[olafurpg]

@danicheg would you still want to add this assertion if assertEquals had a special case for arrays? See #339 and examples

• https://github.com/com-lihaoyi/utest/blob/39e8d4cbc0b34f047c0da43c1013bc276bb73082/utest/src/utest/asserts/Asserts.scala#L87
• https://github.com/zio/zio/blob/e18d6bac8e86eb3ea270c469cc75503704cbe9aa/test/shared/src/main/scala-2.x/zio/test/AssertionVariants.scala#L29

[danicheg]

@olafurpg yeah, I think it's a great idea. If you agree, I'll do a PR today. And then no needing for the extra assertion, I guess.

[olafurpg]

@danicheg Thank you for this contribution and bouncing back and forth on ideas. We just merged #395, which improves the error message when an assertion fails on comparison of two arrays with equal values but different references. In the spirit of keeping the number of assertions small, we're not gonna add assertSameElements. Instead, I encourage you to write such an assertion in your own projects or alternatively override def assertEquals to automatically convert array arguments into normal collections.