add test coverage

[bcoe]

I would love to help add test coverage to this repo, using nyc and potentially babel-plugin-istanbul. Would you accept a pull request for this?

[rauchg]

Sounds great. And a badge!

[arunoda]

And I'd like to see some test cases as well.
@rauchg do you have any plans on how to do testing?
Currently, it's just a few integration test cases.

How about some unit tests for specially stuff in the lib directory?

[bcoe]

@rauchg would you be open to using babel-register for tests, rather than a compile step; or would you prefer to wire up source-maps?

I have a slight preference for babel-register, but can take on either approach (source-maps being slightly more of a hassle).

[rauchg]

@bcoe I tend to use babel-register for tests as well

[nkzawa]

@bcoe @rauchg we don't use babel-register for now since need to compile the source and run tests at the same time in some cases anyway.

[bcoe]

two options for you here:

☝️ implement just the files currently touched by tests -- a less terrifying view of the world.

Instrument everything, a more honest view of the world.

Next question, are there any folders you see there that should be excluded from coverage? CC: @nkzawa, @rauchg

[rauchg]

omg this is so beautiful I want to cry 😭

[bcoe]

@rauchg @nkzawa see #259, I did my best to stay in the spirit of the project's current structure.

[sedubois]

Opened #278 to raise the observation that, besides performance, Jest has built-in test coverage.

[bcoe]

@sedubois Jest uses istanbul-lib-coverage and babel-plugin-istanbul behind the scenes to facilitate its coverage, both libraries that I maintain and are part of #259 . I personally like having nyc in the tool-chain:

• it provides a simple CLI interface for outputting tests in various formats:
  • HTML which helps you dig into where your coverage is lacking.
  • lcov which allows you to pipe it to coveralls, which @rauchg had requested for badges.
• nyc also supports sub-processes, which is useful for instrumenting everything in the next.js/bin.

any ways, I would happily help write some more tests, but my personal preference would be to stick with AVA right now and to get some more tests written; rather than swapping technologies.

@sindresorhus can you speak the the advantages/disadvantages of using AVA vs. Jest for testing a react application, I was reading this document on the technical considerations:

https://github.com/avajs/ava/blob/master/docs/recipes/react.md

[nkzawa]

This tweet makes sense https://twitter.com/sindresorhus/status/774244618057555970
We are trying to introduce babel-core/register but it will gradually make our tests slow.
I think Jest can be a better choice for next.js.

[arunoda]

I also like to move into Jest. Since we don't have many tests, it's better to decide this soon and work on actually writing tests.