我有一个 ScalaTest 2 类,它扩展了 GeneratorDrivenPropertyChecks
,还间接扩展了 FeatureSpec
和 Matchers
(通过我写的扩展那些的特征两个类)。它有这样的代码:
forAll(mySequence) { myItem =>
myItem.applicationID should be (foo.applicationID)
}
编译失败,因为 scalac 说:
[error] APISpec.scala:253: value applicationID is not a member of Seq[com.company.Item]
[error] myItem.applicationID should be (foo.applicationID)
[error] ^
事实证明,至少根据 Eclipse Scala IDE,编译器在 GeneratorDrivenpropertyChecks
中将“forAll”解析为表示此方法:
/**
* Performs a property check by applying the specified property check function to arguments
* supplied by the specified generators.
*
* <p>
* Here's an example:
* </p>
*
* <pre class="stHighlight">
* import org.scalacheck.Gen
*
* // Define your own string generator:
* val famousLastWords = for {
* s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work")
* } yield s
*
* forAll (famousLastWords) { (a: String) =>
* a.length should equal ((a).length)
* }
* </pre>
*
* @param fun the property check function to apply to the generated arguments
*/
def forAll[A](genA: Gen[A], configParams: PropertyCheckConfigParam*)(fun: (A) => Unit)
(implicit
config: PropertyCheckConfig,
shrA: Shrink[A]
) {
// body omitted
}
这不是我想在这里使用的 forAll
方法!
这是 ScalaTest 中的错误吗(即这两个方法不应同时命名为 forAll
)?
我应该如何调用正确的方法?
最佳答案
Is this a bug in ScalaTest
它演示了方法重载的限制。
在an article on selfless traits , Bill Venners 将此模式描述为此类命名冲突的解决方法。
在您的情况下,首选一个重载,因为它是在“派生类”中定义的。
(我认为;我不是这些测试框架的用户,并且生成了其中一个源等,因此测试这不是启动 sbt 并查看代码的简单问题。)
(编辑:scaladoc 说你应该import Inspectors._
。也许你希望用 Matchers
继承它,因为它还建议导入它的同伴,虽然这对我不起作用。如果你确实 import Inspectors._
,你实际上不能通过导入名称来引发过载。)
(编辑:解释命名位:参见规范第 2 章的开头,其中说名称的绑定(bind)具有优先级,并且您继承的名称比您导入的名称具有更高的优先级。)
无论如何,一种解决方案是重新混入 Inspector
,如下所示。
另一种解决方案是通过重命名导入方法:
import Inspectors.{ forAll => iforAll }
尝试选项“-Xprint:typer”、“-Xlog-implicit-conversions”以查看发生了什么很有用。在您的情况下,您的集合通过 ScalaCheck 1.10 中的隐式 View Gen.value
提升为“常量代”。
import org.scalatest._
import org.scalatest.prop._
//class MySpec extends FeatureSpec with Matchers with GeneratorDrivenPropertyChecks
class MySpec extends FeatureSpec with Matchers with GeneratorDrivenPropertyChecks with Inspectors {
case class Foo(id: Int)
val items = 1 to 10 map (Foo.apply(_))
forAll(items) { x => Console println x.id }
}
object Test extends App {
case class Foo(id: Int)
val items = 1 to 10 map (Foo.apply(_))
val sut = new MySpec
sut.forAll(items) { x => Console println x.id }
//sut.forAll[Foo](items) { x => Console println x.i }
}
一些调试输出:
/*
[info] /home/apm/projects/skala-unit-tests/src/test/scala/maqi/MySpec.scala:15: inferred view from scala.collection.immutable.IndexedSeq[maqi.Test.Foo] to org.scalacheck.Gen[?] = scalacheck.this.Gen.value[scala.collection.immutable.IndexedSeq[maqi.Test.Foo]]:(x: scala.collection.immutable.IndexedSeq[maqi.Test.Foo])org.scalacheck.Gen[scala.collection.immutable.IndexedSeq[maqi.Test.Foo]]
> test
[info] Compiling 3 Scala sources to /home/apm/projects/skala-unit-tests/target/scala-2.10/test-classes...
[error] /home/apm/projects/skala-unit-tests/src/test/scala/maqi/MySpec.scala:16: overloaded method value forAll with alternatives:
[error] (genAndNameA: (org.scalacheck.Gen[maqi.Test.Foo], String),configParams: maqi.Test.sut.PropertyCheckConfigParam*)(fun: maqi.Test.Foo => Unit)(implicit config: maqi.Test.sut.PropertyCheckConfig, implicit shrA: org.scalacheck.Shrink[maqi.Test.Foo])Unit <and>
[error] (genA: org.scalacheck.Gen[maqi.Test.Foo],configParams: maqi.Test.sut.PropertyCheckConfigParam*)(fun: maqi.Test.Foo => Unit)(implicit config: maqi.Test.sut.PropertyCheckConfig, implicit shrA: org.scalacheck.Shrink[maqi.Test.Foo])Unit <and>
[error] (nameA: String,configParams: maqi.Test.sut.PropertyCheckConfigParam*)(fun: maqi.Test.Foo => Unit)(implicit config: maqi.Test.sut.PropertyCheckConfig, implicit arbA: org.scalacheck.Arbitrary[maqi.Test.Foo], implicit shrA: org.scalacheck.Shrink[maqi.Test.Foo])Unit <and>
[error] (fun: maqi.Test.Foo => Unit)(implicit config: maqi.Test.sut.PropertyCheckConfig, implicit arbA: org.scalacheck.Arbitrary[maqi.Test.Foo], implicit shrA: org.scalacheck.Shrink[maqi.Test.Foo])Unit
[error] cannot be applied to (scala.collection.immutable.IndexedSeq[maqi.Test.Foo])
[error] sut.forAll[Foo](items) { x => Console println x.i }
[error] ^
*/
关于scalac 在 ScalaTest 测试中发现错误的 forAll 方法,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20383657/