Unable to connect to the NodeJS NATS testcontainer

[jdinsel-xealth]

Expected Behaviour

The example NATS testcontainer should be able to connect.

Actual Behaviour

An error is always returned:

Error connecting to NATS: ConnectionError: connection refused

Testcontainer Logs

  console.log
      testcontainers:containers [f9e8f3a898be] time=2025-05-21T18:27:35.529Z level=INFO msg=starting connection_timeout=1m0s reconnection_timeout=10s request_timeout=10s shutdown_timeout=10m0s remove_retries=10 retry_offset=-1s changes_retry_interval=1s port=8080 verbose=false +0ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [f9e8f3a898be] time=2025-05-21T18:27:35.529Z level=INFO msg=Started address=[::]:8080 +14ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [f9e8f3a898be] time=2025-05-21T18:27:35.529Z level=INFO msg="client processing started" +0ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [f9e8f3a898be] time=2025-05-21T18:27:36.554Z level=INFO msg="client connected" address=172.17.0.1:46164 clients=1 +1s

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [f9e8f3a898be] time=2025-05-21T18:27:36.554Z level=INFO msg="adding filter" type=label values="[org.testcontainers.session-id=194a9424e34a]" +0ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.876320 [INF] Starting nats-server +322ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.876407 [INF]   Version:  2.8.4 +0ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.876409 [INF]   Git:      [66524ed] +0ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.876411 [INF]   Name:     NDO6YNLKKQD7AF2YCUGDL7WUBQMHWS4ADWQKMQU2XZ6BOZMA7WVEXGNH +1ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.876413 [INF]   ID:       NDO6YNLKKQD7AF2YCUGDL7WUBQMHWS4ADWQKMQU2XZ6BOZMA7WVEXGNH +1ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.876420 [WRN] Plaintext passwords detected, use nkeys or bcrypt +0ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.877187 [INF] Listening for client connections on 0.0.0.0:4222 +2ms

      at Logger.debug [as logger] (../node_modules/debug/src/common.js:113:10)

  console.log
      testcontainers:containers [fa463d4bde4d] [1] 2025/05/21 18:27:36.877312 [INF] Server is ready +1ms

Steps to Reproduce

1. Use the steps documented for the NodeJS NATS container
2. Use @nats-io/transport-node for the connect method
3. Execute the test
4. See the error above

Environment Information

• Operating System: MacOS 15.5
• Docker Version: 26.1.5
• Node version: v22.15.0
• Testcontainers version: 10.27.0

[jdinsel-xealth]

I tracked the problem down to an unknown exception within node_modules/@nats-io/transport-node/lib/node_transport.js, but the cause of the exception is not yet apparent.

[joebowbeer]

This also fails for me on MacOS with Rancher Desktop w/Moby

But it works on Windows with Rancher Desktop w/Moby

It does look like the old client library is being used:

testcontainers-node/packages/modules/nats/package.json

Line 32 in 40a945a

"nats": "^2.28.0"

Current is: https://www.npmjs.com/package/@nats-io/transport-node @ 3.0.2

[cristianrgreco]

It does look like the old client library is being used:

testcontainers-node/packages/modules/nats/package.json

Line 32 in 40a945a

"nats": "^2.28.0"

This is a test dependency. You're free to use whatever library you like. If @nats-io/transport-node isn't working with the current NatsContainer, then feel free to raise a PR

[jdinsel-xealth]

Please see the pull request #1009.

[jdinsel-xealth]

The solution to the issue is to follow the troubleshooting steps at https://node.testcontainers.org/supported-container-runtimes/#usage_2. Since I am using Rancher Desktop, I used those settings first, then I added code similar to what is suggested for Colima's "Port forwarding delays." However, the Wait methods did not have an effect.

Instead, I added a 3_000 ms delay to my test case and witnessed it pass for the first time.