Robolectric无法实例化测试类，但单个测试方法可正常执行

问题现象 #

导入和依赖配置均正确的情况下，Robolectric始终无法实例化测试类，导致整个类的测试无法运行；但单独执行每个测试方法时，均可成功通过。

测试代码 #

import androidx.test.ext.junit.runners.AndroidJUnit4
import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test
import org.junit.runner.RunWith

@RunWith(AndroidJUnit4::class)
class MyTet {

    @Test
    fun testAssert() {
        val a = true
        assertTrue(a)
    }
}

build.gradle配置 #

android {
    namespace "com.zga.android"
    testOptions {
        unitTests {
            includeAndroidResources = true
        }
    }
}

dependencies {
    api("androidx.datastore:datastore:1.0.0")
    api "androidx.datastore:datastore-preferences:1.0.0"

    implementation core
    implementation dagger.libs
    implementation room.libs
    ksp dagger.compiler
    ksp room.compiler

    testImplementation project(':test')
    testImplementation unitTesting
    testImplementation 'junit:junit:4.13.2'
    testImplementation 'org.robolectric:robolectric:4.11.1'
    testImplementation 'androidx.test.ext:junit-ktx:1.1.5'
}

错误日志 #

Failed to instantiate test runner class org.robolectric.RobolectricTestRunner
java.lang.RuntimeException: Failed to instantiate test runner class org.robolectric.RobolectricTestRunner
    

    at androidx.test.ext.junit.runners.AndroidJUnit4.throwInitializationError(AndroidJUnit4.java:129)
    at androidx.test.ext.junit.runners.AndroidJUnit4.loadRunner(AndroidJUnit4.java:121)
    at androidx.test.ext.junit.runners.AndroidJUnit4.loadRunner(AndroidJUnit4.java:82)
    at androidx.test.ext.junit.runners.AndroidJUnit4.<init>(AndroidJUnit4.java:56)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Unknown Source)
    at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source)
    at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:104)
    at org.junit.vintage.engine.discovery.DefensiveAllDefaultPossibilitiesBuilder$DefensiveAnnotatedBuilder.buildRunner(DefensiveAllDefaultPossibilitiesBuilder.java:114)
    at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:86)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:70)
    at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:37)
    at org.junit.vintage.engine.discovery.DefensiveAllDefaultPossibilitiesBuilder.runnerForClass(DefensiveAllDefaultPossibilitiesBuilder.java:57)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:70)
    at org.junit.vintage.engine.discovery.ClassSelectorResolver.resolveTestClass(ClassSelectorResolver.java:66)
    at org.junit.vintage.engine.discovery.ClassSelectorResolver.resolve(ClassSelectorResolver.java:47)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.lambda$resolve$2(EngineDiscoveryRequestResolution.java:135)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(Unknown Source)
    at java.base/java.util.ArrayList$ArrayListSpliterator.tryAdvance(Unknown Source)
    at java.base/java.util.stream.ReferencePipeline.forEachWithCancel(Unknown Source)
    at java.base/java.util.stream.AbstractPipeline.copyIntoWithCancel(Unknown Source)
    at java.base/java.util.stream.AbstractPipeline.copyInto(Unknown Source)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
    at java.base/java.util.stream.FindOps$FindOp.evaluateSequential(Unknown Source)
    at java.base/java.util.stream.AbstractPipeline.evaluate(Unknown Source)
    at java.base/java.util.stream.ReferencePipeline.findFirst(Unknown Source)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.resolve(EngineDiscoveryRequestResolution.java:189)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.resolve(EngineDiscoveryRequestResolution.java:126)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.resolveCompletely(EngineDiscoveryRequestResolution.java:92)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.run(EngineDiscoveryRequestResolution.java:83)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolver.resolve(EngineDiscoveryRequestResolver.java:113)
    at org.junit.vintage.engine.discovery.VintageDiscoverer.discover(VintageDiscoverer.java:42)
    at org.junit.vintage.engine.VintageTestEngine.discover(VintageTestEngine.java:64)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discoverEngineRoot(EngineDiscoveryOrchestrator.java:152)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discoverSafely(EngineDiscoveryOrchestrator.java:134)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discover(EngineDiscoveryOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discover(EngineDiscoveryOrchestrator.java:80)
    at org.junit.platform.launcher.core.DefaultLauncher.discover(DefaultLauncher.java:110)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
    at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:110)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:90)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:85)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:62)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.base/java.lang.reflect.Method.invoke(Unknown Source)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
    at jdk.proxy2/jdk.proxy2.$Proxy5.stop(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker$3.run(TestWorker.java:193)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
    at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
    at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:113)
    at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:65)
    at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
    at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
Caused by: java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Unknown Source)
    at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source)
    at androidx.test.ext.junit.runners.AndroidJUnit4.loadRunner(AndroidJUnit4.java:112)
    ... 62 more
Caused by: org.junit.runners.model.InvalidTestClassError: Invalid test class 'com.zga.android.MyTet':
  1. No runnable methods
    at org.junit.runners.ParentRunner.validate(ParentRunner.java:525)
    at org.junit.runners.ParentRunner.<init>(ParentRunner.java:92)
    at org.junit.runners.BlockJUnit4ClassRunner.<init>(BlockJUnit4ClassRunner.java:74)
    at org.robolectric.internal.SandboxTestRunner.<init>(SandboxTestRunner.java:75)
    at org.robolectric.RobolectricTestRunner.<init>(RobolectricTestRunner.java:109)
    at org.robolectric.RobolectricTestRunner.<init>(RobolectricTestRunner.java:104)
    ... 68 more

问题原因 #

错误日志核心提示是No runnable methods，根源是JUnit4与JUnit Jupiter（JUnit5）注解混用：

• 类上使用JUnit4的@RunWith(AndroidJUnit4::class)指定测试运行器
• 测试方法使用JUnit5的org.junit.jupiter.api.Test注解

JUnit4的运行器无法识别JUnit5的@Test，因此运行整个类时会判定无可用测试方法，导致实例化失败；而单独运行方法时，IDE会直接用JUnit5引擎处理，绕过类上的JUnit4配置，因此能正常执行。

解决方案 #

方案1：统一使用JUnit4 #

替换测试方法的@Test为JUnit4版本，保留类上的@RunWith配置：

import androidx.test.ext.junit.runners.AndroidJUnit4
import org.junit.Assert.assertTrue
import org.junit.Test
import org.junit.runner.RunWith

@RunWith(AndroidJUnit4::class)
class MyTet {

    @Test
    fun testAssert() {
        val a = true
        assertTrue(a)
    }
}

方案2：统一使用JUnit5（推荐） #

移除JUnit4的@RunWith，改用Robolectric的JUnit5扩展：

1. 添加Robolectric JUnit5依赖到build.gradle：

testImplementation 'org.robolectric:robolectric-junit5:4.11.1'

2. 修改测试代码：

import org.junit.jupiter.api.Assertions.assertTrue
import org.junit.jupiter.api.Test
import org.robolectric.junit5.RobolectricExtension
import org.junit.jupiter.api.extension.ExtendWith

@ExtendWith(RobolectricExtension::class)
class MyTet {

    @Test
    fun testAssert() {
        val a = true
        assertTrue(a)
    }
}

内容的提问来源于stack exchange，提问作者Varian Wrynn