What is the === (triple-equals) operator in Scala Koans?
ScalaScalatestScala 2.9Scala Problem Overview
I started working my way through the Scala Koans, which is organized around a suite of unit tests with blanks that one needs to fill in. (This idea was modeled after a similar Ruby Koans project.) You start the sbt tool running a test, and it admonishes:
[info] + ***************************************** [info] +
[info] +
[info] +
[info] + Please meditate on koan "None equals None" of suite "AboutEmptyValues" [info] +
[info] +
[info] +
[info] + *****************************************
...and so you go look at this unit test and it says:
test("None equals None") {
assert(None === __)
}
...and, after meditation, you realize that you should fill in the blank like this:
test("None equals None") {
assert(None === None)
}
...and then it moves on to the next unit test.
My question, though, is what is this === operator? I can't seem to find it anywhere. Is this a DSL operator defined in the Scala Koans project itself? Or is it part of the ScalaTest framework? Or in Scala proper?
Scala Solutions
Solution 1 - Scala
This is the triple-equals operator from ScalaTest. Have a look at this page: Getting Started with FunSuite. It says:
> ScalaTest lets you use Scala's assertion syntax, but defines a triple > equals operator (===) to give you better error messages. The following > code would give you an error indicating only that an assertion failed: > > > assert(1 == 2) > > Using triple equals instead would give you the more informative error > message, "1 did not equal 2": > > assert(1 === 2)