Create-react-app: Update Jest

[gaearon]

Jest 16 is coming out soon.
We’ll want to bump the version and include updating snapshots into migration instructions.
cc @cpojer

[fson]

I'd be happy to take this issue when the time comes. Another (smaller) improvement that we can benefit from is that we can remove the custom testRegex (with jsx extension) from the config, because it's going to be the default in Jest 16. (Less config, yay!)

[gaearon]

Btw Jest 16 is a pretty big change (with concurrent reporter) so we’ll want to make sure it works well on Windows before cutting a release.

[fson]

Do you know if React 15.4 is going to be released by the time Jest 16 comes out? It would be nice if we don't need to document the workaround for https://github.com/facebook/react/issues/7386.

Another thing on my wishlist is test renderer traversal / .find() (https://github.com/facebook/react/pull/7516). Snapshot testing is useful on its own, but without traversal, testing any interactions requires also using Enzyme in practice.

[gaearon]

I think 15.4 should be out fairly soon. I can look at find() after it’s out.

[StevenACoffman]

This looks like a duplicate of #851 resolved by PR #858
React 15.4 is not out yet, but Jest 16 is. Not sure if the bugs @fson referenced are worth capturing somewhere else.

[fson]

Jest 16 will be included in 0.7.0, which will be released soon.

[just-boris]

Jest 17 is out now!
It ships some new matchers and also an extension point expect.extend to put your custom ones.

Do I need to create another issue to update used Jest version to 17?

[gaearon]

I think bump to 17 is merged to master.

[just-boris]

That's right. https://github.com/facebookincubator/create-react-app/commit/7e9cb18a5522b20d27ffa9b4443105b55168f1d4

Haven't released yet, though. Looking forward to releasing!

[cpojer]

There'll be another release sometime later this week.