[wip] Jest globals

[developit]

Working on #48.

A useful list of mappings between jest.* and Jasmine is here.

[marvinhagemeister]

The files in the lib folder are not transpiled or inlined. So this will silently skip loading of this file. Moving it to the parent folder fixes it.

[marvinhagemeister]

Looks like those files here are not transpiled at all. Both global and require doesn't exist. Maybe we need to pass this file through webpack?

[developit]

ah - my bad, I meant to hang this off window. Probably better to inject it as a Webpack entry though, yeah.

[andrewiggins]

Really love this idea of Karmatic being a jest that run in real browsers! I thin we can get pretty close to it here!

[andrewiggins]

It looks like all the Jest fake timer APIs are just a thin wrapper around @sinonjs/fake-timers so we could probably just re-implement the timer APIs here on top of @sinonjs/fake-timers since that is browser compatible

[andrewiggins]

Looks like we can also use jest-mock to implement some of these mocking functions. Probably can't do the module mocking functions but for the other core mocking functions, jest-mock doesn't import/require any external modules. I ran its test suite in the browser and it seems to work! So it may not be hard to bring over some of the core mocking functions directly from jest.

Tests I checked: https://github.com/facebook/jest/blob/e8b7f57e05e3c785c18a91556dcbc7212826a573/packages/jest-mock/src/__tests__/index.test.ts#L12-L1399
(do have to remove some TypeScript on lines 13-15 and 228-229

Fake test harness I used to run the tests (which require some node stuff even though the actual implementation does not) (leaving this here for myself in case I want to look at this again):

var s = document.createElement('script');
s.src = 'https://unpkg.com/expect@25.5.0/build-es5/index.js';
document.body.appendChild(s);

window.global = window;
window.module = { exports: {} };
var s = document.createElement('script');
s.src = 'https://unpkg.com/jest-mock@26.3.0/build/index.js';
s.onload = () => {
	setupModuleMocker();
	console.log(moduleMocker);
};
document.body.appendChild(s);

function setupModuleMocker() {
	let ModuleMocker = module.exports.ModuleMocker;
	let moduleMocker = new ModuleMocker(window);

	window.ModuleMocker = ModuleMocker;
	window.moduleMocker = moduleMocker;
	window.jest = {
		fn: moduleMocker.fn.bind(moduleMocker),
	};
}

window.describe = (name, fn) => {
	fn();
};

let beforeEaches = [];
window.beforeEach = (fn) => {
	beforeEaches.push(fn);
};

let testCount = { total: 0, success: 0, failed: 0 };
window.it = window.test = (name, fn) => {
	setupModuleMocker();
	beforeEaches.forEach((fn) => fn());
	try {
		testCount.total++;
		fn();
	} catch (e) {
		testCount.failed++;
		console.error(e);
		console.log(`FAILED: ${name}`);
		return;
	}

	testCount.success++;
	console.log(`SUCCESS: ${name}`);
};

window.vm = {
	createContext() {
		return window;
	},
	runInNewContext(code, context) {
		var f = new Function('runInNewContext_Code', `return eval(\`${code}\`)`);
		return f.call(context);
	},
	runInContext(code, context) {
		return eval(code);
	},
};