关于scala：使用嵌套的forAll在ScalaCheck中生成的对象之间共享元素

Sharing elements between generated objects in ScalaCheck using nested forAll

最近开始使用 Scala 编码，我尝试编写一些基于属性的测试用例。在这里，我试图生成模拟我正在测试的系统的原始数据。目标是首先生成基本元素(ctrl 和 idz)，然后使用这些值生成两个类(A1 和 B1)，最后检查它们的属性。我首先尝试了以下 –

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import org.scalatest._
import prop._
import scala.collection.immutable._
import org.scalacheck.{Gen, Arbitrary}

case class A(
controller: String,
id: Double,
x: Double
)

case class B(
controller: String,
id: Double,
y: Double
)

object BaseGenerators {
val ctrl = Gen.const(“ABC”)
val idz = Arbitrary.arbitrary[Double]
}

trait Generators {
val obj = BaseGenerators

val A1 = for {
controller <– obj.ctrl
id <– obj.idz
x <– Arbitrary.arbitrary[Double]
} yield A(controller, id, x)

val B1 = for {
controller <– obj.ctrl
id <– obj.idz
y <– Arbitrary.arbitrary[Double]
} yield B(controller, id, y)

}

class Something extends PropSpec with PropertyChecks with Matchers with Generators{

property(“Controllers are equal”) {
forAll(A1, B1) {
(a:A,b:B) =>
a.controller should be (b.controller)
}
}

property(“IDs are equal”) {
forAll(A1, B1) {
(a:A,b:B) =>
a.id should be (b.id)
}
}

}

在终端中运行 sbt test 给了我以下 –

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[info] Something:
[info] – Controllers are equal
[info] – IDs are equal *** FAILED ***
[info] TestFailedException was thrown during property evaluation.
[info] Message: 1.1794559135007427E-271 was not equal to 7.871712821709093E212
[info] Location: (testnew.scala:52)
[info] Occurred when passed generated values (
[info] arg0 = A(ABC,1.1794559135007427E-271,-1.6982696700585273E-23),
[info] arg1 = B(ABC,7.871712821709093E212,-8.820696498155311E234)
[info] )

现在很容易看出为什么第二个属性失败了。因为每次我产生 A1 和 B1 我都会为 id 而不是为 ctrl 产生不同的值，因为它是一个常数。以下是我的第二种方法，其中，我创建嵌套 for-yield 来尝试实现我的目标 –

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case class Popo(
controller: String,
id: Double,
someA: Gen[A],
someB: Gen[B]
)

trait Generators {
val obj = for {
ctrl <– Gen.alphaStr
idz <– Arbitrary.arbitrary[Double]
val someA = for {
x <– Arbitrary.arbitrary[Double]
} yield A(ctrl, idz, someA)
val someB = for {
y <– Arbitrary.arbitrary[Double]
} yield B(ctrl, idz, y)
} yield Popo(ctrl, idz, x, someB)
}

class Something extends PropSpec with PropertyChecks with Matchers with Generators{

property(“Controllers are equal”) {
forAll(obj) {
(x: Popo) =>
forAll(x.someA, x.someB) {
(a:A,b:B) =>
a.controller should be (b.controller)
}
}
}

property(“IDs are equal”) {
forAll(obj) {
(x: Popo) =>
forAll(x.someA, x.someB) {
(a:A,b:B) =>
a.id should be (b.id)
}
}
}
}

在第二种方法中运行 sbt test 告诉我所有测试都通过了。

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[info] Something:
[info] – Controllers are equal
[info] – IDs are equal
[info] ScalaTest
[info] Run completed in 335 milliseconds.
[info] Total number of tests run: 2
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 2, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.

有没有更好/替代的方法来重现我想要的结果？嵌套 forAll 对我来说似乎相当笨拙。如果我的依赖图中有 R -> S -> … V -> W 用于共享元素的对象，那么我将不得不创建尽可能多的嵌套 forAll.