JUnit 5: Support `@Nested` classes

[jbduncan]

If one runs an @TestParameterInjectorTest test method inside an inner class annotated with JUnit 5's @Nested annotation, it throws the following stack trace.

Example

import com.google.testing.junit.testparameterinjector.junit5.TestParameterInjectorTest;
import com.google.testing.junit.testparameterinjector.junit5.TestParameters;
import org.junit.jupiter.api.Nested;

import static org.junit.jupiter.api.Assertions.assertEquals;

class OuterTests {

  @Nested
  class NestedTests {

    @TestParameterInjectorTest
    @TestParameters("{input: foo, output: bar}")
    void test(String input, String output) {
      assertEquals(output.length(), input.length());
    }
  }
}

Stack trace

java.lang.IllegalStateException: No matching test parameter annotation found for parameter of type OuterTests in method/constructor OuterTests$NestedTests(OuterTests)
java.lang.AssertionError: java.lang.IllegalStateException: No matching test parameter annotation found for parameter of type OuterTests in method/constructor OuterTests$NestedTests(OuterTests)
	at com.google.testing.junit.testparameterinjector.junit5.ExecutableValidationResult.assertValid(ExecutableValidationResult.java:66)
	at com.google.testing.junit.testparameterinjector.junit5.TestParameterInjectorExtension.validateTestMethodAndConstructor(TestParameterInjectorExtension.java:67)
	at com.google.testing.junit.testparameterinjector.junit5.TestParameterInjectorExtension.provideTestTemplateInvocationContexts(TestParameterInjectorExtension.java:49)
	at org.junit.jupiter.engine.descriptor.TestTemplateTestDescriptor.lambda$execute$0(TestTemplateTestDescriptor.java:106)
	at java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:273)
	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
	at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596)
	at org.junit.jupiter.engine.descriptor.TestTemplateTestDescriptor.execute(TestTemplateTestDescriptor.java:110)
	at org.junit.jupiter.engine.descriptor.TestTemplateTestDescriptor.execute(TestTemplateTestDescriptor.java:44)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
	at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
	at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:99)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:79)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:75)
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:62)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
	at jdk.proxy1/jdk.proxy1.$Proxy2.stop(Unknown Source)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker$3.run(TestWorker.java:193)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:113)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:65)
	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
Caused by: java.lang.IllegalStateException: No matching test parameter annotation found for parameter of type OuterTests in method/constructor OuterTests$NestedTests(OuterTests)
	at com.google.testing.junit.testparameterinjector.junit5.TestParameterAnnotationMethodProcessor.validateMethodOrConstructorParameters(TestParameterAnnotationMethodProcessor.java:619)
	at com.google.testing.junit.testparameterinjector.junit5.TestParameterAnnotationMethodProcessor.validateConstructor(TestParameterAnnotationMethodProcessor.java:518)
	at com.google.testing.junit.testparameterinjector.junit5.TestMethodProcessorList.lambda$validateConstructor$4(TestMethodProcessorList.java:134)
	at com.google.common.collect.Iterators$6.transform(Iterators.java:829)
	at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:52)
	at com.google.common.collect.Iterators.tryFind(Iterators.java:780)
	at com.google.common.collect.Iterables.tryFind(Iterables.java:708)
	at com.google.common.collect.FluentIterable.firstMatch(FluentIterable.java:476)
	at com.google.testing.junit.testparameterinjector.junit5.TestMethodProcessorList.validateConstructor(TestMethodProcessorList.java:135)
	... 85 more

[nymanjens]

This is a known issue. We have an internal bug open for this, but not prioritized yet because we don't use JUnit5 internally and it's hard to get a sense of the demand for this outside of Google.

[jbduncan]

@nymanjens Oh, I'm glad this was reported internally, too! Thanks for letting me know. And no worries, I've inferred from Google's open source code over the years that you're still stuck on JUnit 4, so I completely understand that other things have taken and will take priority. :)

Would you be open to a contribution? I know this isn't the usual policy for Guava et al, but I'm unsure about this project.

In the meantime, I'll use JUnit 5's built-in @ParameterizedTest or junit-pioneer's @CartesianTest instead.

[nymanjens]

Would you be open to a contribution?

Yes, although this @Nested stuff might need some changes to the code that is shared between junit4 and junit5 internally (it is copied to two different locations before exporting it to github), and so it might be a bit harder to backport, but certainly not impossible.

[jbduncan]

Okay, good to know, thanks for the warning. I'll see if I can take a stab at this in the near future, then.

[jbduncan]

@nymanjens Actually it doesn't seem I'll be able to look into this any time soon, so feel free to assign this story to someone else.