Now playing in ScalaTest master...

gistfile1.scala

//
// This is not yet at a good point for a milestone release, but I've been doing a lot of
// work to try and improve equality and containership checks in ScalaTest and Scalactic. One part of it is
// that I figured out how to get equal, be, and contain matchers to participate in the kind of type checking
// that previously only worked with === and should ===. The difficulty was that equal, be, and contain
// can be used with logical operators and, or, and not (whereas === did not). Here are some examples:
//

scala> 1 shouldBe 1L

scala> 1 shouldBe "one"
<console>:20: error: could not find implicit value for parameter
    evidence: org.scalactic.enablers.EvidenceThat[String]#CanEqual[Int]
              1 shouldBe "one"
                ^

scala> 1L shouldEqual 1

scala> "one" shouldEqual 1
<console>:20: error: could not find implicit value for parameter
    evidence: org.scalactic.enablers.EvidenceThat[Int]#CanEqual[String]
              "one" shouldEqual 1
                    ^

scala> List(1, 2, 3) should (have length 3 and not be Vector(3, 2, 1))

scala> List(1, 2, 3) should (have length 3 and not be Set(3, 2, 1))
<console>:20: error: could not find implicit value for parameter 
    typeClass2: org.scalactic.enablers.EvidenceThat[scala.collection.immutable.Set[Int]]#CanEqual[List[Int]]
              List(1, 2, 3) should (have length 3 and not be Set(3, 2, 1))
                            ^

scala> List(1, 2) should contain (2)

scala> List(1, 2) should contain ("two")
<console>:20: error: could not find implicit value for parameter 
    ypeClass1: org.scalactic.enablers.EvidenceThat[String]#CanBeContainedIn[List[Int]]
              List(1, 2) should contain ("two")
                         ^

scala> List(1, 2) should contain oneOf (2, 3)

scala> List(1, 2) should contain oneOf ("two", "three")
<console>:20: error: could not find implicit value for parameter
    evidence: org.scalactic.enablers.EvidenceThat[String]#CanBeContainedIn[List[Int]]
              List(1, 2) should contain oneOf ("two", "three")
                                        ^

scala> List(1, 2) should (have length 2 and contain oneOf (2, 3))

scala> List(1, 2) should (have length 2 and contain oneOf ("two", "three"))
<console>:20: error: could not find implicit value for parameter
    typeClass2: org.scalactic.enablers.EvidenceThat[String]#CanBeContainedIn[List[Int]]
              List(1, 2) should (have length 2 and contain oneOf ("two", "three"))
                         ^