Help configuring Dape to debug TestNG (Java) tests

[ghost]

Could you please help me figure out how to configure a Dape template to debug Java TestNG tests?

You could find my current progress here:
https://gist.github.com/oscarvarto/d9cb5aa7e6d1ed3df729760d22d15779

I couldn't connect the DAP debugger (no matter what I tried). I got a message like:

• Unable to connect to dap server at localhost:5005 *
• Connection is configurable by host' and port' keys *

Please, help!!

[Storm-Dev6]

Hi @oscarvarto 👋

I saw your question and wanted to share how to configure Dape to debug TestNG tests with Java. The main issue seems to be that the Java process isn't listening for debugger connections on the specified port (e.g., localhost:5005).

✅ Step-by-step solution

1. Start Java with JDWP debugging enabled
   You need to run your Java process with the debugger agent enabled, like this:

java -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005 \
-cp your-classpath-here \
org.testng.TestNG your-testng.xml

suspend=y: makes Java wait until the debugger connects before starting

address=5005: Java will listen on this port for the debugger

Make sure this command is run before attaching Dape.

2. Configure dape.json
   Your Dape configuration should use "request": "attach" to connect to the running Java process:

{
"configurations": [
{
"name": "Debug TestNG",
"type": "java",
"request": "attach",
"host": "localhost",
"port": 5005
}
]
}

🧪 Test the setup
1 Run the Java process with the JDWP options above

2 Open Dape and select your "Debug TestNG" configuration

3 SStart debugging — it should now connect to the Java process successfully

ℹ️ Notes
Make sure port 5005 isn't already used by something else

You can change the port in both the Java command and Dape config if needed

The suspend=y flag is helpful to ensure the debugger attaches before the test starts

Let me know if you’d like a full example with testng.xml and Dape config — happy to help further!

Hope this works for you 🙌

[ghost]

I tried again, but failed. Sorry, I am giving up.

[Storm-Dev6]

Never givup!

[ghost]

I've been a fervent Emacs user, and spent a lot of time configuring it. But I also want to get things done and get my peace of mind as well as my sleep. I'll probably get back to Emacs, but I don't think I'll do it for programming/debugging.