Test fails: TypeError: Cannot read property 'length' of undefined

[mscheper]

So I really am just getting started with React, have zero experience with Webpack, and I'm feeling kinda rusty with NodeJS, so forgive me if I'm doing something ignorant. But I followed the instructions in the README file, and got the following error when I ran the tests:

> react-way-getting-started@1.0.0 test /(my-parent)/react-way-getting-started
> jest

Using Jest CLI v0.4.19
 FAIL  src/app/components/__tests__/Cart.spec.js
TypeError: Cannot read property 'length' of undefined
  at maybeReadMore_ (_stream_readable.js:438:18)
  at /(my-parent)/react-way-getting-started/node_modules/jest-cli/src/lib/FakeTimers.js:342:7
  at nextTickCallbackWith0Args (node.js:420:9)
  at process._tickCallback (node.js:349:13)

/(my-parent)/react-way-getting-started/node_modules/jest-cli/node_modules/node-worker-pool/Worker.js:106
    throw new Error('Received unexpected data from child process: ' + data);
    ^

Error: Received unexpected data from child process: {
  "error": "TypeError: Cannot read property 'length' of undefined\n  at onwriteDrain (_stream_writable.js:362:12)\n  at afterWrite (_stream_writable.js:352:5)\n  at /(my-parent)/react-way-getting-started/node_modules/jest-cli/src/lib/FakeTimers.js:342:7\n  at nextTickCallbackWith0Args (node.js:420:9)\n  at Immediate._tickCallback [as _onImmediate] (node.js:349:13)\n  at processImmediate [as _immediateCallback] (timers.js:383:17)\n"
}

  at Worker._onStdout (/(my-parent)/react-way-getting-started/node_modules/jest-cli/node_modules/node-worker-pool/Worker.js:106:11)
  at emitOne (events.js:77:13)
  at Socket.emit (events.js:169:7)
  at readableAddChunk (_stream_readable.js:153:18)
  at Socket.Readable.push (_stream_readable.js:111:10)
  at Pipe.onread (net.js:536:20)

npm ERR! Test failed.  See above for more details.

I'm using node v4.5.0 and webpack 1.13.2 under Mint 17.

[ador]

Same error here, with webpack 3.10.3 and node v6.7.0.