scala：如何在 specs2 中实现这个匹配器

Question

我有以下方法：

def save(entity: A): Either[List[Error],A] + {....

我想使用 specs2 进行测试

我想在未指定必填字段时测试是否存在特定错误，如下所示：

val noNickname = User(
  nickname = "",
  name = "new name",
)

noNickname.save must beLeft.like {
  case errors => {
    atLeastOnceWhen(errors) {
      case error => {
        error.errorCode must equalTo(Error.REQUIRED)
        error.field must equalTo("nickname")
      }
    }
  }
}

它工作正常，但我想定义自己的匹配器以使其不那么冗长，如下所示：

noNickname.save must haveError.like {
    case error => {
      error.errorCode must equalTo(Error.REQUIRED)
      error.field must equalTo("nickname")
    }
  }
}

我查看了文档 (http://etorreborre.github.com/specs2/guide/org.specs2.guide.Matchers.html#Matchers) 但我不知道如何定义自定义匹配器喜欢 haveError.like

Answer 1

这里你的代码有一些改变使它编译：

case class Error(errorCode: String, field: String)
def save[A](entity: A): Either[List[Error],A] = Left(List(Error("REQUIRED", "nickname")))
case class User(nickname: String, name: String)

val noNickname = User(nickname = "", name = "new name")

"save noNickName" >> {
  save(noNickname) must haveError.like {
    case error => {
      error.errorCode must equalTo("REQUIRED")
      error.field must equalTo("nickname")
    }
  }
}

def haveError[T] = new ErrorMatcher[T]

class ErrorMatcher[T] extends Matcher[Either[List[T], _]] {
  def apply[S <: Either[List[T], _]](value: Expectable[S]) = 
    result(value.value.left.toOption.isDefined, 
      value.description + " is Left",
      value.description + " is not Left",
      value)

  def like[U](f: PartialFunction[T, MatchResult[U]]) = 
    this and partialMatcher(f)

  private def partialMatcher[U](f: PartialFunction[T, MatchResult[U]]) = 
    new Matcher[Either[List[T], _]] {

    def apply[S <: Either[List[T], _]](value: Expectable[S]) = {
      // get should always work here because it comes after the "and"
      val errors = value.value.left.toOption.get
      val res = atLeastOnceWhen[T, U](errors)(f)
      result(res.isSuccess,
        value.description+" is Left[T] and "+res.message,
        value.description+" is Left[T] but "+res.message,
        value)
    }
  }
}

请注意，匹配器是在 Either[List[T], _] 各处定义的。

我还想知道如果您没有找到预期的错误消息时返回的失败消息，当部分函数失败时它们可能不是很明确。

因此，您可能希望使用包含匹配器。像这样：

"save noNickName" >> {
  save(noNickname) must haveError.containing(Error("REQUIRED", "nickname"))
}

// I'm reusing the beLeft matcher here
def haveError[T]: Matcher[Either[List[T], _]] = beLeft

// and using an implicit conversion to extend it
implicit def toErrorListMatcher[T](m: Matcher[Either[List[T], _]]): ErrorListMatcher[T] =    
  new ErrorListMatcher[T](m)

class ErrorListMatcher[T](m: Matcher[Either[List[T], _]]) {
  def containing(t: T) =
    // the 'contain' matcher is adapted to take in an 
    // Either[List[T], _] and work on its left part
    m and contain(t) ^^ ((e: Either[List[T], _]) => e.left.toOption.get)
}

[更新]

第一个解决方案（使用atLeastOnceWhen 和一个偏函数）可以与第二个解决方案（使用隐式）和beLike 匹配器相结合，以获得现有 specs2 代码的最大可重用性：

def haveError[T]: Matcher[Either[List[T], _] = beLeft

implicit def toErrorListMatcher[T](m: Matcher[Either[List[T], _]]): ErrorListMatcher[T] = 
  new ErrorListMatcher[T](m)

class ErrorListMatcher[T](m: Matcher[Either[List[T], _]]) {
  // beLike checks one element
  // beLike.atLeastOnce transforms that matcher on a 
  // matcher on a sequence of elements
  def like[S](f: PartialFunction[T, MatchResult[S]]) = {
    m and beLike(f).atLeastOnce ^^ ((e: Either[List[T], _]) => e.left.toOption.get)
}