Debugging Jest tests in a MonoRep with VSCode

README.md

Debugging Jest tests in a MonoRep with VSCode

If you're writing unit tests, there will be times when the ability to debug specific tests will come in handy. This is how you set up a debugging profile for VSCode.

---

Set up VSCode

At the root of your repo create a .vscode folder, and dump these files in it:

• launch.json
• debugJest.js
• jestDebugger.js

debugJest.js

#!/usr/bin/env node

/* eslint-disable no-console, import/no-dynamic-require */

const spawn = require('react-dev-utils/crossSpawn');


// Makes the script crash on unhandled rejections instead of silently
// ignoring them. In the future, promise rejections that are not handled will
// terminate the Node.js process with a non-zero exit code.
process.on('unhandledRejection', (err) => {
  throw err;
});

const argv = process.argv.slice(2);
const nodeArgs = argv.slice(0, 1);
const jestArgs = argv.slice(1);
const result = spawn.sync(
  'node',
  nodeArgs
    .concat(require.resolve(`${__dirname}/jestDebugger.js`))
    .concat(jestArgs),
  { stdio: 'inherit' }
);

if (result.signal) {
  if (result.signal === 'SIGKILL') {
    console.log(
      'The build failed because the process exited too early. ' +
        'This probably means the system ran out of memory or someone called ' +
        '`kill -9` on the process.'
    );
  } else if (result.signal === 'SIGTERM') {
    console.log(
      'The build failed because the process exited too early. ' +
        'Someone might have called `kill` or `killall`, or the system could ' +
        'be shutting down.'
    );
  }
  process.exit(1);
}
process.exit(result.status);

jestDebugger.js

/* eslint-disable no-console, import/no-dynamic-require */

const jest = require('jest');

process.env.BABEL_ENV = 'test';
process.env.NODE_ENV = 'test';
process.env.PUBLIC_URL = '';

const argv = process.argv.slice(2);
const fileArgNdx = argv.length - 1;
const currPackage = argv[fileArgNdx].match(/.*\/packages\/[\w-]+\//)[0];
const jestConf = require(`${currPackage}/package.json`).jest;
const currTestFile = argv.pop().split(currPackage)[1];

jestConf.rootDir = currPackage;
jestConf.collectCoverage = false;

argv.push(
  '--config',
  JSON.stringify(jestConf),
  currTestFile, // the last arg has to be the watched file
);
// @remove-on-eject-end
jest.run(argv);

launch.json

{
  "configurations": [
    {
      "name": "Debug Jest Tests",
      "type": "node",
      "request": "launch",
      "runtimeExecutable": "${workspaceFolder}/.vscode/debugJest.js",
      "args": [
        "--runInBand",
        "--no-cache",
        "--env=jsdom",
        "--watchAll",
        "${file}",
      ],
      "protocol": "inspector",
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen"
    }
  ]
}