Refactor test suite to Jest (+watch +coverage)

[ferrannp]

Related to #406

• All tests from test folder are now using Jest and they only depend on it (no sinon, no expect). There is a configuration in package.json to tell Jest only run tests inside test folder
• --watch mode is working (see gif below)
• Running npm run test-coverage will create html page into coverage folder (so it also solves Cover reports no longer being generated in gluestick (resolve with Jest) #345)
• Debugging with Chrome, just need to follow these steps: https://facebook.github.io/jest/docs/troubleshooting.html#tests-are-failing-and-you-don-t-know-why

This is a pull request to get familiar also with Jest and play with it (specially with the --watch mode). If we are happy with it, we could also introduce Jest to the generated app with gluestick so we can get rid of istambul (solving #333), mocha, karma, sinon and expect (maybe even more if we needed special babel deps for it).

Watch mode

Debugging

[sethbattin]

Followon from #322 : my first thought is this: https://youtrack.jetbrains.com/issue/WEB-14979 <- jest does not have direct webstorm support yet. :|

But that's really just ide-sugar anyway. As long as there is a cli entry point and file saving triggers watch mode, then we're good regardless of explicit support. And if debugging via devtools works, then that solves the other use case.

I will try this one out in earnest later in the day.

[zamotany]

Debugging with Chrome, just need to follow these steps: https://facebook.github.io/jest/docs/troubleshooting.html#tests-are-failing-and-you-don-t-know-why

They use node-inspector but we are removing it in favour of node --inspect (#322).

[zamotany]

https://youtu.be/1cfA87h_1hI
on Ubuntu 16.04

Notice that debugger; statement in test doesn't trigger break.

[toddw]

This looks really cool!

Looks like there are some issues in the build: https://travis-ci.org/TrueCar/gluestick/builds/193784640#L387

[toddw]

The tests are broken specifically when --watch is passed so it is likely something that just needs to be updated in our tests

[ferrannp]

All test seem to PASS but for some reason the build gets stuck (not exiting with error or success). I am not sure if those console.error(s) or some throwings that are happening in some tests are the cause. I need to investigate/try more on this.

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Edit 1:

Ok, I found that the test that makes Travis to fail is new.test.js, that tests promts the user to a question Do you wish to continue? and this keeps Jest to be hanging. I need to investigate a solution for this.

The other thing that concerns me is that all these tests are actually hitting the disk and creating/removing files. Probably, we want unit tests to mock this behaviour. See the exact example with fs https://facebook.github.io/jest/docs/manual-mocks.html

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Edit 2:

Ok I have the build passing: https://travis-ci.org/TrueCar/gluestick/builds/194489121

The problem is that I had to run it manually since it looks like that PRs to TrueCar:v1 are not triggering builds in Travis. Can you check this @toddw? I guess it is just to change travis.yml in develop.

[toddw]

I updated .travis.yml so it should now include the v1 branch

[toddw]

The other thing that concerns me is that all these tests are actually hitting the disk and creating/removing files. Probably, we want unit tests to mock this behaviour.

Yeah, since a major part of the CLI is creating files, it does write and read from disk during tests. I'm sure we could mock this but it might get tricky to validate the CLI is actually doing what it should. We are totally open to any suggestions here

[ferrannp]

So build is green :). About hitting the disk, I think that for now is fine. Maybe in the future we want to try something but it does not feel as a bottleneck right now. I think this PR is ready as it is @toddw.

[toddw]

works great! Thanks @ferrannp

I was not able to get Chrome inspector to work yet but that's a different issue.
Related (#406 (comment))

[ferrannp]

@toddw you should be able when #445 is merged.