JUnit5：如何重复失败的测试？

Question

许多公司遵循的一种做法是重复不稳定测试，直到通过 x 次（连续或总共）。如果它被执行了 n 次并且没有通过至少 x 次它被标记为失败。

TestNG 通过以下注释支持它：

@Test(invocationCount = 5, successPercentage = 40)

如何使用 JUnit5 实现类似的功能？

JUnit5 中有类似的注解，叫做@RepeatedTest(5)，但它不是有条件地执行的。

Answer 1

好的，我花了一点时间整理了一个小例子，说明如何使用 TestTemplateInvocationContextProvider、ExecutionCondition 和 TestExecutionExceptionHandler 扩展点做到这一点。

我能够处理失败测试的方法是将它们标记为“已中止”，而不是让它们完全失败（这样整个测试执行不会认为它失败）并且只有在我们不能失败时才使测试失败获得最少的成功运行次数。如果最小数量的测试已经成功，那么我们还将剩余的测试标记为“禁用”。在ExtensionContext.Store 中跟踪测试失败，以便可以在每个位置查找状态。

这是一个非常粗略的示例，肯定存在一些问题，但希望可以作为如何编写不同注释的示例。我最终用 Kotlin 编写了它：

@Retry-esque 注释松散地基于 TestNG 示例：

import org.junit.jupiter.api.TestTemplate
import org.junit.jupiter.api.extension.ExtendWith

@TestTemplate
@Target(AnnotationTarget.FUNCTION)
@ExtendWith(RetryTestExtension::class)
annotation class Retry(val invocationCount: Int, val minSuccess: Int)

TestTemplateInvocationContext 用于模板化测试：

import org.junit.jupiter.api.extension.Extension
import org.junit.jupiter.api.extension.TestTemplateInvocationContext

class RetryTemplateContext(
  private val invocation: Int,
  private val maxInvocations: Int,
  private val minSuccess: Int
) : TestTemplateInvocationContext {
  override fun getDisplayName(invocationIndex: Int): String {
    return "Invocation number $invocationIndex (requires $minSuccess success)"
  }

  override fun getAdditionalExtensions(): MutableList<Extension> {
    return mutableListOf(
      RetryingTestExecutionExtension(invocation, maxInvocations, minSuccess)
    )
  }
}

TestTemplateInvocationContextProvider @Retry 注释的扩展：

import org.junit.jupiter.api.extension.ExtensionContext
import org.junit.jupiter.api.extension.ExtensionContextException
import org.junit.jupiter.api.extension.TestTemplateInvocationContext
import org.junit.jupiter.api.extension.TestTemplateInvocationContextProvider
import org.junit.platform.commons.support.AnnotationSupport
import java.util.stream.IntStream
import java.util.stream.Stream

class RetryTestExtension : TestTemplateInvocationContextProvider {
  override fun supportsTestTemplate(context: ExtensionContext): Boolean {
    return context.testMethod.map { it.isAnnotationPresent(Retry::class.java) }.orElse(false)
  }

  override fun provideTestTemplateInvocationContexts(context: ExtensionContext): Stream<TestTemplateInvocationContext> {
    val annotation = AnnotationSupport.findAnnotation(
        context.testMethod.orElseThrow { ExtensionContextException("Must be annotated on method") },
        Retry::class.java
    ).orElseThrow { ExtensionContextException("${Retry::class.java} not found on method") }

    checkValidRetry(annotation)

    return IntStream.rangeClosed(1, annotation.invocationCount)
        .mapToObj { RetryTemplateContext(it, annotation.invocationCount, annotation.minSuccess) }
  }

  private fun checkValidRetry(annotation: Retry) {
    if (annotation.invocationCount < 1) {
      throw ExtensionContextException("${annotation.invocationCount} must be greater than or equal to 1")
    }
    if (annotation.minSuccess < 1 || annotation.minSuccess > annotation.invocationCount) {
      throw ExtensionContextException("Invalid ${annotation.minSuccess}")
    }
  }
}

表示重试的简单data class（在本示例中使用ParameterResolver 注入到测试用例中）。

data class RetryInfo(val invocation: Int, val maxInvocations: Int)

Exception 用于表示重试失败：

import java.lang.Exception

internal class RetryingTestFailure(invocation: Int, cause: Throwable) : Exception("Failed test execution at invocation #$invocation", cause)

实现ExecutionCondition、ParameterResolver和TestExecutionExceptionHandler的主要扩展。

import org.junit.jupiter.api.extension.ConditionEvaluationResult
import org.junit.jupiter.api.extension.ExecutionCondition
import org.junit.jupiter.api.extension.ExtensionContext
import org.junit.jupiter.api.extension.ParameterContext
import org.junit.jupiter.api.extension.ParameterResolver
import org.junit.jupiter.api.extension.TestExecutionExceptionHandler
import org.opentest4j.TestAbortedException

internal class RetryingTestExecutionExtension(
  private val invocation: Int,
  private val maxInvocations: Int,
  private val minSuccess: Int
) : ExecutionCondition, ParameterResolver, TestExecutionExceptionHandler {
  override fun evaluateExecutionCondition(
    context: ExtensionContext
  ): ConditionEvaluationResult {
    val failureCount = getFailures(context).size
    // Shift -1 because this happens before test
    val successCount = (invocation - 1) - failureCount
    when {
      (maxInvocations - failureCount) < minSuccess -> // Case when we cannot hit our minimum success
        return ConditionEvaluationResult.disabled("Cannot hit minimum success rate of $minSuccess/$maxInvocations - $failureCount failures already")
      successCount < minSuccess -> // Case when we haven't hit success threshold yet
        return ConditionEvaluationResult.enabled("Have not ran $minSuccess/$maxInvocations successful executions")
      else -> return ConditionEvaluationResult.disabled("$minSuccess/$maxInvocations successful runs have already ran. Skipping run $invocation")
    }
  }

  override fun supportsParameter(
    parameterContext: ParameterContext,
    extensionContext: ExtensionContext
  ): Boolean = parameterContext.parameter.type == RetryInfo::class.java

  override fun resolveParameter(
    parameterContext: ParameterContext,
    extensionContext: ExtensionContext
  ): Any = RetryInfo(invocation, maxInvocations)

  override fun handleTestExecutionException(
    context: ExtensionContext,
    throwable: Throwable
  ) {

    val testFailure = RetryingTestFailure(invocation, throwable)
    val failures: MutableList<RetryingTestFailure> = getFailures(context)
    failures.add(testFailure)
    val failureCount = failures.size
    val successCount = invocation - failureCount
    if ((maxInvocations - failureCount) < minSuccess) {
      throw testFailure
    } else if (successCount < minSuccess) {
      // Case when we have still have retries left
      throw TestAbortedException("Aborting test #$invocation/$maxInvocations- still have retries left",
        testFailure)
    }
  }

  private fun getFailures(context: ExtensionContext): MutableList<RetryingTestFailure> {
    val namespace = ExtensionContext.Namespace.create(
      RetryingTestExecutionExtension::class.java)
    val store = context.parent.get().getStore(namespace)
    @Suppress("UNCHECKED_CAST")
    return store.getOrComputeIfAbsent(context.requiredTestMethod.name, { mutableListOf<RetryingTestFailure>() }, MutableList::class.java) as MutableList<RetryingTestFailure>
  }
}

然后，测试消费者：

import org.junit.jupiter.api.DisplayName

internal class MyRetryableTest {
  @DisplayName("Fail all retries")
  @Retry(invocationCount = 5, minSuccess = 3)
  internal fun failAllRetries(retryInfo: RetryInfo) {
    println(retryInfo)
    throw Exception("Failed at $retryInfo")
  }

  @DisplayName("Only fail once")
  @Retry(invocationCount = 5, minSuccess = 4)
  internal fun succeedOnRetry(retryInfo: RetryInfo) {
    if (retryInfo.invocation == 1) {
      throw Exception("Failed at ${retryInfo.invocation}")
    }
  }

  @DisplayName("Only requires single success and is first execution")
  @Retry(invocationCount = 5, minSuccess = 1)
  internal fun firstSuccess(retryInfo: RetryInfo) {
    println("Running: $retryInfo")
  }

  @DisplayName("Only requires single success and is last execution")
  @Retry(invocationCount = 5, minSuccess = 1)
  internal fun lastSuccess(retryInfo: RetryInfo) {
    if (retryInfo.invocation < 5) {
      throw Exception("Failed at ${retryInfo.invocation}")
    }
  }

  @DisplayName("All required all succeed")
  @Retry(invocationCount = 5, minSuccess = 5)
  internal fun allRequiredAllSucceed(retryInfo: RetryInfo) {
    println("Running: $retryInfo")
  }

  @DisplayName("Fail early and disable")
  @Retry(invocationCount = 5, minSuccess = 4)
  internal fun failEarly(retryInfo: RetryInfo) {
    throw Exception("Failed at ${retryInfo.invocation}")
  }
}

IntelliJ 中的测试输出如下所示：

我不知道从TestExecutionExceptionHandler.handleTestExecutionException 中抛出TestAbortedException 是否应该中止测试，但我在这里使用它。

Answer 2

你可以试试这个 junit 5 的扩展。

<dependency>
    <groupId>io.github.artsok</groupId>
    <artifactId>rerunner-jupiter</artifactId>
    <version>LATEST</version>
</dependency> 

例子：

     /** 
        * Repeated three times if test failed.
        * By default Exception.class will be handled in test
        */
       @RepeatedIfExceptionsTest(repeats = 3)
       void reRunTest() throws IOException {
           throw new IOException("Error in Test");
       }


       /**
        * Repeated two times if test failed. Set IOException.class that will be handled in test
        * @throws IOException - error occurred
        */
       @RepeatedIfExceptionsTest(repeats = 2, exceptions = IOException.class)
       void reRunTest2() throws IOException {
           throw new IOException("Exception in I/O operation");
       }


       /**
        * Repeated ten times if test failed. Set IOException.class that will be handled in test
        * Set formatter for test. Like behavior as at {@link org.junit.jupiter.api.RepeatedTest}
        * @throws IOException - error occurred
        */
       @RepeatedIfExceptionsTest(repeats = 10, exceptions = IOException.class, 
       name = "Rerun failed test. Attempt {currentRepetition} of {totalRepetitions}")
       void reRunTest3() throws IOException {
           throw new IOException("Exception in I/O operation");
       }

       /**
       * Repeated 100 times with minimum success four times, then disabled all remaining repeats.
       * See image below how it works. Default exception is Exception.class
       */
       @DisplayName("Test Case Name")
       @RepeatedIfExceptionsTest(repeats = 100, minSuccess = 4)
       void reRunTest4() {
            if(random.nextInt() % 2 == 0) {
                throw new RuntimeException("Error in Test");
            }
       }

在 IDEA 上查看：

至少成功四次，然后禁用所有其他：

您还可以将@RepeatedIfExceptionsTest 与@DisplayName 混合使用

source -> github

Answer 3

如果您是通过 Maven 运行测试，那么使用 Surefire，您需要使用 rerunFailingTestsCount 自动重新运行失败的测试。

但是，从 2.21.0 开始，这不适用于 JUnit 5（仅 4.x）。但希望它会在下一个版本中得到支持。

Answer 4

如果您碰巧使用Gradle 构建工具运行测试，则可以使用Test Retry Gradle 插件。这将重新运行每个失败的测试一定次数，如果总体上发生了太多失败，则可以选择使构建失败。

plugins {
    id 'org.gradle.test-retry' version '1.2.0'
}

test {
    retry {
        maxRetries = 3
        maxFailures = 20 // Optional attribute
    }
}