junit-team/junit5 · warning · UncheckedIOException

Failed to close file system for

Error message

Failed to close file system for ${jarUri}

What it means

UncheckedIOException thrown by CloseablePath.ManagedFileSystem.close() when FileSystem.close() fails during teardown of a managed jar filesystem (the reference count dropped to zero). The jarUri and the original IOException are attached. This is a resource-release-time failure, distinct from open-time failure (error 89).

Solutions

1. Audit code for manual FileSystem.close() calls on jars that JUnit manages
2. Reduce parallel test fan-out that touches the same jar
3. Raise OS file-handle limits (ulimit -n) if exhaustion is the cause
4. Ensure antivirus/build tooling is not locking the jar

try {
    closeablePath.close();
} catch (UncheckedIOException e) {
    // log; usually safe to continue at teardown - the FS is being torn down anyway
}

When it happens

Trigger: Closing a jar FileSystem whose underlying file handle is already closed, concurrently closed, or otherwise unavailable; OS-level resource exhaustion at teardown.

Common situations: Concurrent test execution racing on the same jar filesystem; nested CloseablePath usage closing the FS prematurely; file-handle leaks exhausting the OS limit; antivirus or build-tool locking on Windows.

Related errors

• Failed to create file system for
• Failed to read contents of
• Error redirecting stderr to file
• Error redirecting stdout and stderr to file
• Error redirecting stdout to file

AI-assisted analysis of junit-team/junit5@f070c699a0 (2026-08-11). Data as JSON: /api/errors/e7b8ba7786965dae. Report an issue: GitHub.

Appendix: source

Thrown at junit-platform-commons/src/main/java/org/junit/platform/commons/util/CloseablePath.java:131

		private ManagedFileSystem retain() {
			referenceCount.incrementAndGet();
			return this;
		}

		private @Nullable ManagedFileSystem release() {
			if (referenceCount.decrementAndGet() == 0) {
				close();
				return null;
			}
			return this;
		}

		private void close() {
			try {
				fileSystem.close();
			}
			catch (IOException e) {
				throw new UncheckedIOException("Failed to close file system for " + jarUri, e);
			}
		}
	}

	interface FileSystemProvider {
		FileSystem newFileSystem(URI uri) throws IOException;
	}
}

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