Debugging

TIP

When debugging tests you might want to use --test-timeout CLI argument to prevent tests from timing out when stopping at breakpoints.

VSCode

Quick way to debug tests in VSCode is via JavaScript Debug Terminal. Open a new JavaScript Debug Terminal and run npm run test or vitest directly. this works with any code ran in Node, so will work with most JS testing frameworks

You can also add a dedicated launch configuration to debug a test file in VSCode:

{
  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
    {
      "type": "node",
      "request": "launch",
      "name": "Debug Current Test File",
      "autoAttachChildProcesses": true,
      "skipFiles": ["<node_internals>/**", "**/node_modules/**"],
      "program": "${workspaceRoot}/node_modules/vitest/vitest.mjs",
      "args": ["run", "${relativeFile}"],
      "smartStep": true,
      "console": "integratedTerminal"
    }
  ]
}

Then in the debug tab, ensure 'Debug Current Test File' is selected. You can then open the test file you want to debug and press F5 to start debugging.

IntelliJ IDEA

Create a 'Node.js' run configuration. Use the following settings to run all tests in debug mode:

Setting	Value
Working directory	/path/to/your-project-root
JavaScript file	./node_modules/vitest/vitest.mjs
Application parameters	run --pool forks

Then run this configuration in debug mode. The IDE will stop at JS/TS breakpoints set in the editor.

Node Inspector, e.g. Chrome DevTools

Vitest also supports debugging tests without IDEs. However this requires that tests are not run parallel. Use one of the following commands to launch Vitest.

# To run in a single worker
vitest --inspect-brk --pool threads --poolOptions.threads.singleThread

# To run in a single child process
vitest --inspect-brk --pool forks --poolOptions.forks.singleFork

If you are using Vitest 1.1 or higher, you can also just provide --no-file-parallelism flag:

# If pool is unknown
vitest --inspect-brk --no-file-parallelism

Once Vitest starts it will stop execution and wait for you to open developer tools that can connect to Node.js inspector. You can use Chrome DevTools for this by opening chrome://inspect on browser.

In watch mode you can keep the debugger open during test re-runs by using the --poolOptions.threads.isolate false options.