JUnit5 test fails with: memory file system does not support #toFile()

[TobseF]

After adding a @MemoryTempDir annotation in my test, it wont't start anymore.
It seems that Gradle is not able to finish the test setup.

Test Setup: Kotlin JVM project with Gradle 8.7

⚡ Full Stacktrace

memory file system does not support #toFile()
java.lang.UnsupportedOperationException: memory file system does not support #toFile()
	at com.github.marschall.memoryfilesystem.AbstractPath.toFile(AbstractPath.java:74)
	at org.junit.jupiter.engine.extension.TempDirectory.getPathOrFile(TempDirectory.java:260)
	at org.junit.jupiter.engine.extension.TempDirectory.lambda$injectFields$3(TempDirectory.java:147)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1092)
	at org.junit.jupiter.engine.extension.TempDirectory.injectFields(TempDirectory.java:139)
	at org.junit.jupiter.engine.extension.TempDirectory.injectInstanceFields(TempDirectory.java:131)
	at org.junit.jupiter.engine.extension.TempDirectory.lambda$beforeEach$0(TempDirectory.java:114)
	at java.base/java.util.Collections$SingletonList.forEach(Collections.java:4966)
	at org.junit.jupiter.engine.extension.TempDirectory.beforeEach(TempDirectory.java:114)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeBeforeEachCallbacks$2(TestMethodTestDescriptor.java:167)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeBeforeMethodsOrCallbacksUntilExceptionOccurs$6(TestMethodTestDescriptor.java:203)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeBeforeMethodsOrCallbacksUntilExceptionOccurs(TestMethodTestDescriptor.java:203)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeBeforeEachCallbacks(TestMethodTestDescriptor.java:166)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:133)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:69)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$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$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$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.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:119)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:94)
	at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:89)
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:62)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
	at jdk.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)

[marschall]

Can you provide a bit more context? I assume you use @MemoryTempDir from memoryfilesystem-junit-provider.

On what type did you put the @MemoryTempDir annotation? Was it a Path or a File? I assume it was a File. If so that is not supported and can not be supported. This is mentioned in the API Javadoc of Path.toFile()

Throws:
UnsupportedOperationException - if this Path is not associated with the default provider

The reason for this is that the implementation is hard wired to the operating system file system. You might be confused as java.io.File has a #fs variable of type FileSystem. However this if of type java.io.FileSystem, not of type java.nio.file.FileSystem.

Long story short @MemoryTempDir only supports Path, it can not be made to support File. I'll update the docs.

Is there a specific reason you need java.io.File?

[scordio]

The user experience will be improved in JUnit 5.11, see junit-team/junit-framework#3910 and junit-team/junit-framework#3921.

[marschall]

The user experience will be improved in JUnit 5.11, see junit-team/junit5#3910 and junit-team/junit5#3921.

Awesome, thanks a lot. Didn't even have to file an issue. Looking forward to 5.11.

[marschall]

Closing, with 5.11 you should not get

org.junit.jupiter.api.extension.ParameterResolutionException: Failed to resolve parameter [java.io.File arg0] in method [void com.github.marschall.memoryfilesystem.junit.MemoryTempDirTests.injectFile(java.io.File)]: Failed to create default temp directory
	at java.util.ArrayList.forEach(ArrayList.java:1259)
	at java.util.ArrayList.forEach(ArrayList.java:1259)
Caused by: org.junit.jupiter.api.extension.ExtensionConfigurationException: Failed to create default temp directory
	... 2 more
Caused by: org.junit.platform.commons.PreconditionViolationException: temp directory with non-default file system cannot be injected into java.io.File target
	... 2 more