TestRenderer warns if flushThrough is passed the wrong params

[bvaughn]

This was silently passing before, when it probably should have failed harder (in case we forgot to expect-to-equal).

The resulting test failures now will not be as pretty (wrt diff highlighting) but it's more foolproof.

[bvaughn]

This PR caught this (actual) mistake from master.

[pull-bot]

Details of bundled changes.

Comparing: 76e0707...51d563e

react-test-renderer

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
react-test-renderer.development.js	+0.2%	+0.2%	339.29 KB	339.87 KB	73.33 KB	73.51 KB	UMD_DEV
react-test-renderer.production.min.js	🔺+0.4%	🔺+0.8%	45.57 KB	45.77 KB	14.06 KB	14.18 KB	UMD_PROD
react-test-renderer.development.js	+0.2%	+0.3%	330.12 KB	330.7 KB	70.59 KB	70.77 KB	NODE_DEV
react-test-renderer.production.min.js	🔺+0.5%	🔺+0.9%	44.67 KB	44.88 KB	13.59 KB	13.72 KB	NODE_PROD
ReactTestRenderer-dev.js	+0.2%	+0.3%	335.96 KB	336.61 KB	70.17 KB	70.37 KB	FB_WWW_DEV

Generated by 🚫 dangerJS

[acdlite]

Looks good. Left some nits on the error messages but in practice I don't think it matters since we probably expect folks to build their own helper on top of this so they get a nicer diff.

[acdlite]

Typo?

[bvaughn]

Yargh

[acdlite]

Isn't the loop below sufficient?

[bvaughn]

Yeah. I thought this error message might be more readable, but you're right- it's unnecessary.

[acdlite]

Maybe we should switch our tests to use a global flushThrough method?

global.flushThrough = (testRendererRoot, expectedValues) => {
  try {
    testRendererRoot.unstable_flushThrough(expectedValues);
  } catch (e) {
    expect(e.actualValues).toEqual(expectedValues);
  }
}

[bvaughn]

Yeah, maybe...

Before

After

In some ways, this error message is better (because of the nice diff coloring) but in other ways, it's worse- because there's no message/context. Just a couple of arrays that don't match.

We also have to remember to use it, which we may not.

Either way, this change lets us simplify all of the calls like:

expect(renderer.unstable_flushThrough([...])).toEqual([...]);

Down to:

renderer.unstable_flushThrough([...]);

Which seems like a win, since we also sometimes forgot to add those .toEqual checks.

[bvaughn]

Maybe I can just call jest-diff manually, like I do in the toWarnDev matcher...

global.flushThrough = (testRendererRoot, expectedValues) => {
  try {
    testRendererRoot.unstable_flushThrough(expectedValues);
  } catch (error) {
    throw new Error(error.message + '\n\n' + jestDiff(expectedValues, error.actualValues));
  }
}

Results in error messages like:

But something about this still seems too awkward to do, because your code would end up looking like:

flushThrough(renderer, ['A:1']);
// Expectations...
renderer.unstable_flushAll();