如何为单个Scala Mockito测试用例启用宽松模式保留冗余桩？

被测试代码 #

import concurrent.{ExecutionContext, Future}

trait Backend {
  def verifyUser(): Future[Unit]
  def accounts(): Future[String]
}

class Service(backend: Backend) {
  private implicit val executor: ExecutionContext = ExecutionContext.global
  def accounts(): Future[String] =
    (for (_ <- backend.verifyUser(); accs <- backend.accounts()) yield accs)
    .recover { case ex => s"failed: ${ex.getMessage}" }
}

测试代码 #

import org.scalatest._
import matchers.should
import flatspec.AsyncFlatSpec
import org.mockito.scalatest.AsyncIdiomaticMockito

class ServiceTest extends AsyncFlatSpec with AsyncIdiomaticMockito with should.Matchers {
  private trait Fixture {
    lazy val backend: Backend = mock[Backend]
    lazy val service: Service = new Service(backend)
  }

  it should "return the reason of a failure" in {
    val fixture = new Fixture {}
    import fixture._
    backend.verifyUser() returns Future.failed(new RuntimeException("verifyUser"))
    backend.accounts()   returns Future.failed(new RuntimeException("accounts"))
    service.accounts() map { result =>
      result should startWith ("failed: ")
    }
  }
}

报错信息 #

Unnecessary stubbings detected.
Clean & maintainable test code requires zero unnecessary code.
Following stubbings are unnecessary (click to navigate to relevant line of code):

1. -> at ServiceTest.$anonfun$new$1(StrictStubbingTest.scala:25)
   Please remove unnecessary stubbings or use 'lenient' strictness. More info: javadoc for UnnecessaryStubbingException class.
   org.mockito.exceptions.misusing.UnnecessaryStubbingException:

由于verifyUser()执行失败后，accounts()方法不会被调用，导致对应的桩被Mockito判定为冗余，抛出上述异常。要求保留两个桩的同时让测试通过，且仅为当前测试用例启用宽松模式。

有两种精准控制的实现方式：

方式一：为单个冗余桩标记宽松模式 #

直接对不会被触发的backend.accounts()桩使用lenient()包装，仅让这个桩跳过未调用校验，其他桩仍保持Mockito的严格校验规则：

it should "return the reason of a failure" in {
  val fixture = new Fixture {}
  import fixture._
  backend.verifyUser() returns Future.failed(new RuntimeException("verifyUser"))
  // 为该冗余桩启用宽松模式，忽略未调用检查
  lenient(backend.accounts()) returns Future.failed(new RuntimeException("accounts"))
  service.accounts() map { result =>
    result should startWith ("failed: ")
  }
}

方式二：为当前测试块启用全局宽松模式 #

如果需要让当前测试用例中的所有桩都跳过未调用校验，可以用lenient代码块包裹所有stub定义：

it should "return the reason of a failure" in {
  val fixture = new Fixture {}
  import fixture._
  // 该代码块内的所有桩都启用宽松模式
  lenient {
    backend.verifyUser() returns Future.failed(new RuntimeException("verifyUser"))
    backend.accounts() returns Future.failed(new RuntimeException("accounts"))
  }
  service.accounts() map { result =>
    result should startWith ("failed: ")
  }
}

两种方式都能满足需求，方式一更精准（仅针对冗余桩），方式二更适合需要批量设置的场景。

内容的提问来源于stack exchange，提问作者danissimo