Migrate to Jest (mostly)

• Karma + Jasmine + PhantomJS is slow.
• PhantomJS is unstable. (CI has been failing since b5b8e29 due to PhantomJS crashing in the middle of tests; I am unable to reproduce this behavior locally.) Jasmine

I’d love to migrate the whole project to Jest because it’s much faster. Unfortunately a couple of components (AutoSizer and CellMeasurer) depend on a more robust browser than JSDOM and currently that’s all that Jest supports.

So my proposal for now:

• Split NPM test:unit script into 2 child tasks: test:unit:jasmine and test:unit:jest
• Rename all tests that can be run in Jest from *.test.js to *.jest.js

[elevine]

On a related note, this seems to work for anyone who needs to mock out AutoSizer for snapshot testing:

// __mocks__/react-virtualized.js
import React from 'react';

const reactVirtualized = jest.genMockFromModule('react-virtualized');

const MockAutoSizer = () => {
  return <div />;
};

reactVirtualized.AutoSizer = MockAutoSizer;

module.exports = reactVirtualized;

Then at the top of your test file, do: jest.mock('react-virtualized');

Update: This doesn’t seem to render out the children. I’ve created a Gist where I’ll keep working to find an ideal solution: https://gist.github.com/elevine/69a27e067032c53d64d66f4f56e978cc

[bvaughn]

No problem. That’s interesting to learn! I’m not using Mocha so that may also account for some of the difference in our impressions.

I’ve been really impressed by Jest’s mocking and snapshot functionalities. I hope to take advantage of both going forward.

Also worth pointing out that PhantomJS has been crashing for me in CI environment for weeks. Could not reproduce locally. Overall seemed very flaky. Despite its limitations, JSDom seems more robust.

Given its limitations for that matter- I’m surprised you would see faster results from Mocha+PhantomJS than from Jest+JSDom just because of the browsers alone.

Oh well. 😁 Glad you started this conversation either way. It’s interesting.

On Jan 28, 2017 1:04 PM, “Olivier Tassinari” [e-mail] wrote:

I’d love to learn more about

We have around 1800+ tests, we have tried to migrate to jest, but that was way too slow. We reverted to our Mocha + Karma + PhantomJS test suite.

Iterating on tests (running in watch mode) was.

I guess that’s what I was looking for! We haven’t looked at the iterating response time. That need more investigation from my part. Thanks.

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