feat: integration testing helper

[bcoe]

What is this?

Creates an integration testing helper that's exposed via next/test/helper. This is useful for upstream apps that would like to test next.js using an integration server.

why? I'm OCD about unit-testing, and as far as I can tell existing tools like Enzyme don't work perfectly for next.js, since next.js' rendering helpers have quite a bit of magic (good magic, mind you):

  const doc = createElement(Document, {
    __NEXT_DATA__: {
      component,
      errorComponent,
      props,
      pathname,
      query,
      err: (err && dev) ? errorToJSON(err) : null
    },
    dev,
    staticMarkup,
    ...docProps
  })

The API

async setup():

Sets up the integration testing application.

SKIP_BUILD=1 can be provided, to avoid building an application between test runs -- this can be useful when you're adding unit-tests to an existing codebase.

async teardown():

Cleanup the integration testing application.

async render(path, query, req, res, opts):

Helper for rendering application:

The order of arguments is different than render/renderToHTML, to better server the most common use-case:

render('/some-path', {q: 'some params'})

The query-string module is used to magically populate req.url.

[coveralls]

Coverage increased (+2.08%) to 60.487% when pulling 5bbc458 on bcoe:test-helper into fe962b1 on zeit:master.

[nkzawa]

👍 I wonder if this helper can be a different library.

[rauchg]

same

[bcoe]

@nkzawa if so, want to have dibs and create something in the zeit org?

[rauchg]

@bcoe done, check your notifications. Closing for now

[bcoe]

@rauchg awesome, I'll get a repo stubbed out tomorrow.