allow access to chrome coverage from test-script

[schrotie]

Hey, I love mocha-headless-chrome, thanks!

The main reason I use it is because I use modern tech which requires Chrome if I don't want to transpile and polyfill (and the polyfills seem pretty hairy to get running in jsdom). I'm hell bent on keeping my dev process clean, i.e. no transpilation or polyfills during dev if I can help it. Istanbul requires tranpilation. However, I found a way to get Chromes built-in coverage information and use that in an assert in my tests. Just had to add a tiny little bit of hack to you stuff, I hope you consider it :-) My test.html then contains this script:

mocha.setup('bdd');
chai.should();

describeCoverageTest();
((window.puppeteerStartCoverage && puppeteerStartCoverage()) || Promise.resolve())
.then(listTests)
.then(importTests)
.then(() => {
	mocha.checkLeaks();
	mocha.run();
});

function listTests() {return fetch('/test').then(res => res.text());}

function importTests(text) {return Promise.all(
	text.match(/(\w+)\.mjs/g).map(file => import(`./${file}`))
);}

function describeCoverageTest() {
	if(!window.puppeteerStartCoverage) return;
	after(done => {
		puppeteerStopCoverage()
		.then(coverage => {
			const sq = /shadowQuery\.mjs/;
			coverage = coverage.js.filter(el => sq.test(el.url))[0];
			let totalBytes = coverage.text.length, usedBytes = 0;
			for(let range of coverage.ranges) usedBytes += range.end - range.start - 1;
			coverage = usedBytes / totalBytes;
			try{coverage.should.be.above(0.99);}
			catch(e) {done(); throw new Error(`Insufficient coverage: ${coverage}`);}
			done();
		});
	});
}

[schrotie]

Or maybe just hand the whole puppeteer.page down to the test script?