When running Java unit tests via Test Runner for Java in WSL2, the UI stays stuck at: Resolving launch configuration...

[inkpark]

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)

[github-actions]

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:

  1. Open <USER>/.vscode/extensions/vscjava.vscode-java-test-0.44.0/client/out/src/server.js.
  2. Replace:

     const port = await getPort();
     server.listen(port, "127.0.0.1", callback);

     with:

     server.listen(0, "127.0.0.1", callback);

  3. Reload VS Code and rerun your tests.

Duplicate Issues

• No exact duplicates found for version 0.44.0.

Other references with high confidence

• Tests cannot be launched (#1481) – Reports tests stuck on “Resolving launch configuration” in WSL2; fixed in v0.37.1.

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]

btw I'd like to work on this issue.