案例类列表中的Scalatest Double等价

Question

我有 Double值将相似，但不准确。通常我会这样做:

val a: Double = ???
val b: Double = ???

a shouldEqual b +- 0.25

如果我只是比较单个案例类，我会这样做:

case class Data(label: String, value: Double)
val a: Data = ???
val b: Data = ???
a.value shouldEqual b.value +- 0.25

就我而言，我有一个案例类实例列表，并希望将它们与它们的容差进行比较 value属性:

val output = Seq(Data("a", 1.1), Data("b", 1.2))
val expected = Seq(Data("a", 0.9), Data("b", 1.1))
output should contain theSameElementsInOrderAs expected

当然，那会归档，因为 value属性不完全匹配。我需要的是这样的:

output should contain theSameElementsInOrderAs expected +- 0.25

Answer 1

我最终定义了一个自定义 Matcher我的 Seq[Data]类型:

trait CustomMatcher {

  class SeqDataContainsTheSameElementsInOrderAs(expected: Seq[Data]) {

    override def apply(left: Seq[Data]): MatchResult = {

      // ... do other checks like comparing the length and such

      val bad = left.zip(expected).filter(t => {
        val difference = Math.abs(t._1.value - t._2.value)
        difference > TOLERANCE // Declare this somewhere
      })

      // Return the MatchResult, you will probably want to give better error messages than this
      MatchResult(
        bad.isEmpty,
        s"""Some of the values were not equal""",
        s"""Everything was equal"""
      )
    }

    def customContainTheSameElementsInOrderAs(expected: Seq[Data]) = new SeqDataContainsTheSameElementsInOrderAs(expected)
  }
}

然后我像这样使用它:

output should customContainTheSameElementsInOrderAs(expected)