Add the options in the Support for debugging NodeJS tests section from to your project's .bazelrc file to add support for debugging NodeJS programs.

Using the --config=debug command line option with bazel will set a number of flags that are specified there are useful for debugging. See the comments under Support for debugging NodeJS tests for details on the flags that are set.

Use --config=debug with bazel test as follow,

bazel test --config=debug //test:...

or with bazel run,

bazel run --config=debug //test:test1

to also turn on the NodeJS inspector agent which will break before any user code starts. You should then see,

Executing tests from //test:test1
Debugger listening on ws://
For help, see:

when the test is run.

To inspect with Chrome DevTools 55+, open chrome://inspect in a Chromium-based browser and attach to the waiting process. A Chrome DevTools window should open and you should see Debugger attached. in the console.

See for more details.

Debugging with VS Code

With the above configuration you can use VS Code as your debugger. You will first need to configure your .vscode/launch.json:

      "type": "node",
      "request": "attach",
      "name": "Attach nodejs_binary",
      "internalConsoleOptions": "neverOpen",
      "sourceMapPathOverrides": {
        "../*": "${workspaceRoot}/*",
        "../../*": "${workspaceRoot}/*",
        "../../../*": "${workspaceRoot}/*",
        "../../../../*": "${workspaceRoot}/*",
        "../../../../../*": "${workspaceRoot}/*",
        // do as many levels here as needed for your project

We use sourceMapPathOverrides here to rewrite the source maps produced by ts_library so that breakpoints line up with the source maps. Once configured start your process with

bazel run --config=debug //test:test1

Then hit F5 which will start the VS Code debugger with the Attach nodejs_binary configuration. VS Code will immediatenly hit a breakpoint to which you can continue and debug using all the normal debug features provided.