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When running Java unit tests via Test Runner for Java in WSL2, the UI stays stuck at: Resolving launch configuration... #1854
Description
Bug Description
When running Java unit tests via Test Runner for Java, the UI stays stuck at:
Resolving launch configuration...
Root Cause
VS Code Test Runner for Java 0.44.0 creates a local socket server before launching tests. It uses get-port to pre-select a port, then closes the probe socket and rebinds to the same port on
127.0.0.1. In WSL/Windows port environments, this "pre-select then rebind" pattern causes massive EADDRINUSE failures.
Evidence from VS Code extension log:
Error: listen EADDRINUSE: address already in use 127.0.0.1:46129
Error: listen EADDRINUSE: address already in use 127.0.0.1:46423
Error: listen EADDRINUSE: address already in use 127.0.0.1:46333
Error: listen EADDRINUSE: address already in use 127.0.0.1:46049
Error: listen EADDRINUSE: address already in use 127.0.0.1:45865
Reproduction
The problematic pattern in the extension:
const port = await getPort(); // Step 1: reserve a port
server.listen(port, "127.0.0.1", callback); // Step 2: rebind to same port
In the affected environment, ~96 out of 100 such attempts fail.
Suggested Fix
Replace the two-step port selection with direct port allocation:
server.listen(0, "127.0.0.1", callback); // OS auto-assigns a free port
This approach achieves 0 failures in the same environment.
Environment
- OS: Windows + WSL
- VS Code Test Runner for Java: 0.44.0
- Multiple JDKs installed (Java 8, 21, 25)
Activity
github-actions commentedon Apr 11, 2026
Hi inkpark, I'm an AI Support assistant here to help with your issue. While the team reviews your request, I wanted to provide some possible tips and documentation that might help you in the meantime.
Suggested Workarounds
Upgrade to the latest “Test Runner for Java” extension (>= 0.45.x) once available. A similar “stuck at Resolving launch configuration” bug on WSL2 was reported and fixed in #1481.
As a temporary local patch, edit the port‐binding logic in your installed extension:
<USER>/.vscode/extensions/vscjava.vscode-java-test-0.44.0/client/out/src/server.js.Duplicate Issues
Other references with high confidence
The team will respond to your issue shortly. I hope these suggestions are helpful in the meantime. If this comment helped you, please give it a 👍. If the suggestion was not helpful or incorrect, please give it a 👎. Your feedback helps us improve!
inkpark commentedon Apr 12, 2026
btw I'd like to work on this issue.
fix: use listen(0) for OS auto-port-allocation instead of getPort pre…
fix: use listen(0) for OS auto-port-allocation instead of getPort (#1855