sapper/test/apps/preloading/test.ts

import * as assert from 'assert';
import * as puppeteer from 'puppeteer';
import { build } from '../../../api';
import { wait } from '../../utils';
import { AppRunner } from '../AppRunner';

declare const fulfil: () => Promise<void>;

describe('preloading', function() {
	this.timeout(10000);

	let runner: AppRunner;
	let page: puppeteer.Page;
	let base: string;

	// helpers
	let start: () => Promise<void>;
	let prefetchRoutes: () => Promise<void>;
	let title: () => Promise<string>;

	// hooks
	before(async () => {
		await build({ cwd: __dirname });

		runner = new AppRunner(__dirname, '__sapper__/build/server/server.js');
		({ base, page, start, prefetchRoutes, title } = await runner.start());
	});

	after(() => runner.end());

	it('serializes Set objects returned from preload', async () => {
		await page.goto(`${base}/preload-values/set`);

		assert.equal(await title(), 'true');

		await start();
		assert.equal(await title(), 'true');
	});

	it('prevent crash if preload return nothing', async () => {
		await page.goto(`${base}/preload-nothing`);

		await start();
		await wait(50);

		assert.equal(await title(), 'Page loaded');
	});

	it('bails on custom classes returned from preload', async () => {
		await page.goto(`${base}/preload-values/custom-class`);

		assert.equal(await title(), '42');

		await start();
		assert.equal(await title(), '42');
	});

	it('sets preloading true when appropriate', async () => {
		await page.goto(base);
		await start();
		await prefetchRoutes();

		await page.click('a[href="slow-preload"]');

		assert.ok(await page.evaluate(() => !!document.querySelector('progress')));

		await page.evaluate(() => fulfil());
		assert.ok(await page.evaluate(() => !document.querySelector('progress')));
	});

	it('runs preload in root component', async () => {
		await page.goto(`${base}/preload-root`);
		assert.equal(await title(), 'root preload function ran: true');
	});

	it('cancels navigation if subsequent navigation occurs during preload', async () => {
		await page.goto(base);
		await start();
		await prefetchRoutes();

		await page.click('a[href="slow-preload"]');
		await wait(100);
		await page.click('a[href="foo"]');

		assert.equal(page.url(), `${base}/foo`);
		assert.equal(await title(), 'foo');

		await page.evaluate(() => fulfil());
		await wait(100);
		assert.equal(page.url(), `${base}/foo`);
		assert.equal(await title(), 'foo');
	});

	it('navigates to prefetched urls', async () => {
		await page.goto(base);
		await start();
		await prefetchRoutes();

		await page.hover('a[href="prefetch/qwe"]');
		await wait(100);
		await page.hover('a[href="prefetch/xyz"]');
		await wait(100);

		await page.click('a[href="prefetch/qwe"]');
		await wait(50);

		assert.equal(
			await title(),
			'qwe'
		);

		await page.goto(`${base}/prefetch`);
		await wait(50);

		assert.equal(
			await title(),
			'prefetch'
		);
	});
});