Scalatest案例類別清單中的雙等同案件

Question

我有Double值在價值上相似，但不是確切的。通常情況下，我會做：

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

a shouldEqual b +- 0.25 

如果我只是比較單一的情況下類，我會做：

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

在我的情況，我有case類實例的列表，並想用比較寬容他們的value屬性：

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 

當然，這會文件，因爲value屬性不完全匹配。我需要的是這樣的：

output should contain theSameElementsInOrderAs expected +- 0.25 

Answer 1

我結束了定義自定義Matcher我Seq[Data]類型：

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) 
    } 
} 

然後我用它喜歡：

output should customContainTheSameElementsInOrderAs(expected) 

Answer 2

你可以只去

forAll(output.zipAll(expected, null, null)) { 
    case (a, b) => a.value shouldEqual b.value +- 0.25 
} 

使用zipAll因爲zip會錯誤地成功時的長度不匹配，但錯誤信息你會得到這樣ISN太不好。