/
onLCP-test.js
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/
onLCP-test.js
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/*
* Copyright 2020 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const assert = require('assert');
const {beaconCountIs, clearBeacons, getBeacons} = require('../utils/beacons.js');
const {browserSupportsEntry} = require('../utils/browserSupportsEntry.js');
const {imagesPainted} = require('../utils/imagesPainted.js');
const {stubForwardBack} = require('../utils/stubForwardBack.js');
const {stubVisibilityChange} = require('../utils/stubVisibilityChange.js');
describe('onLCP()', async function() {
// Retry all tests in this suite up to 2 times.
this.retries(2);
let browserSupportsLCP;
before(async function() {
browserSupportsLCP = await browserSupportsEntry('largest-contentful-paint');
});
beforeEach(async function() {
await clearBeacons();
// TODO(philipwalton): not sure why this is needed, but it may be related
// to: https://bugs.chromium.org/p/chromium/issues/detail?id=1034080
await browser.url('about:blank');
});
it('reports the correct value on hidden (reportAllChanges === false)', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp');
// Wait until all images are loaded and fully rendered.
await imagesPainted();
// Load a new page to trigger the hidden state.
await browser.url('about:blank');
await beaconCountIs(1);
assertStandardReportsAreCorrect(await getBeacons());
});
it('reports the correct value on hidden (reportAllChanges === true)', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?reportAllChanges=1');
// Wait until all images are loaded and fully rendered.
await imagesPainted();
// Load a new page to trigger the hidden state.
await browser.url('about:blank');
await beaconCountIs(2);
assertFullReportsAreCorrect(await getBeacons());
});
it('reports the correct value on input (reportAllChanges === false)', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp');
// Wait until all images are loaded and fully rendered.
await imagesPainted();
// Click on the h1.
const h1 = await $('h1');
await h1.click();
await beaconCountIs(1);
assertStandardReportsAreCorrect(await getBeacons());
});
it('reports the correct value on input (reportAllChanges === true)', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?reportAllChanges=1');
// Wait until all images are loaded and fully rendered.
await imagesPainted();
// Click on the h1.
const h1 = await $('h1');
await h1.click();
await beaconCountIs(2);
assertFullReportsAreCorrect(await getBeacons());
});
it('accounts for time prerendering the page', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?prerender=1');
// Wait until all images are loaded and fully rendered.
await imagesPainted();
const activationStart = await browser.execute(() => {
return performance.getEntriesByType('navigation')[0].activationStart;
});
// Load a new page to trigger the hidden state.
await browser.url('about:blank');
await beaconCountIs(1);
const [lcp] = await getBeacons();
assert.strictEqual(lcp.entries[0].startTime - activationStart, lcp.value);
assert.strictEqual(lcp.navigationType, 'prerender');
});
it('does not report if the browser does not support LCP (including bfcache restores)', async function() {
if (browserSupportsLCP) this.skip();
await browser.url('/test/lcp');
// Wait until all images are loaded and fully rendered.
await imagesPainted();
// Click on the h1.
const h1 = await $('h1');
await h1.click();
// Scroll down
const footer = await $('footer');
await footer.scrollIntoView();
// Simulate a tab switch and switch back, which triggers reporting in
// browsers that support the API.
await stubVisibilityChange('hidden');
await stubVisibilityChange('visible');
// Wait a bit to ensure no beacons were sent.
await browser.pause(1000);
assert.strictEqual((await getBeacons()).length, 0);
await clearBeacons();
await stubForwardBack();
// Wait a bit to ensure no beacons were sent.
await browser.pause(1000);
assert.strictEqual((await getBeacons()).length, 0);
});
it('does not report if the document was hidden at page load time', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?hidden=1');
await stubVisibilityChange('visible');
// Click on the h1.
const h1 = await $('h1');
await h1.click();
// Wait a bit to ensure no beacons were sent.
await browser.pause(1000);
const beacons = await getBeacons();
assert.strictEqual(beacons.length, 0);
});
it('does not report if the document changes to hidden before the first render', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?invisible=1');
await stubVisibilityChange('hidden');
await stubVisibilityChange('visible');
// Click on the h1.
const h1 = await $('h1');
await h1.click();
// Wait a bit to ensure no beacons were sent.
await browser.pause(1000);
const beacons = await getBeacons();
assert.strictEqual(beacons.length, 0);
});
it('stops reporting after the document changes to hidden (reportAllChanges === false)', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?imgDelay=0&imgHidden=1');
// Wait for a frame to be painted.
await browser.executeAsync((done) => requestAnimationFrame(done));
await stubVisibilityChange('hidden');
await stubVisibilityChange('visible');
await browser.execute(() => {
document.querySelector('img').hidden = false;
});
// Click on the h1.
const h1 = await $('h1');
await h1.click();
// Wait a bit to ensure no additional beacons were sent.
await browser.pause(1000);
await beaconCountIs(1);
const [lcp1] = await getBeacons();
assert(lcp1.value > 0);
assert.strictEqual(lcp1.name, 'LCP');
assert.strictEqual(lcp1.value, lcp1.delta);
assert.strictEqual(lcp1.entries.length, 1);
assert.strictEqual(lcp1.entries[0].element, 'h1');
assert.match(lcp1.navigationType, /navigate|reload/);
});
it('stops reporting after the document changes to hidden (reportAllChanges === true)', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?reportAllChanges=1&imgDelay=0&imgHidden=1');
await beaconCountIs(1);
const [lcp] = await getBeacons();
assert(lcp.value > 0);
assert.strictEqual(lcp.name, 'LCP');
assert.strictEqual(lcp.value, lcp.delta);
assert.strictEqual(lcp.entries.length, 1);
assert.strictEqual(lcp.entries[0].element, 'h1');
assert.match(lcp.navigationType, /navigate|reload/);
await clearBeacons();
await stubVisibilityChange('hidden');
await stubVisibilityChange('visible');
await browser.execute(() => {
document.querySelector('img').hidden = false;
});
// Wait a bit to ensure no beacons were sent.
await browser.pause(1000);
const beacons = await getBeacons();
assert.strictEqual(beacons.length, 0);
});
it('reports if the page is restored from bfcache', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp');
// Wait until all images are loaded and fully rendered.
await imagesPainted();
const h1 = await $('h1');
await h1.click();
await beaconCountIs(1);
assertStandardReportsAreCorrect(await getBeacons());
await clearBeacons();
await stubForwardBack();
await beaconCountIs(1);
const [lcp2] = await getBeacons();
assert(lcp2.value > 0); // Greater than the image load delay.
assert(lcp2.id.match(/^v2-\d+-\d+$/));
assert.strictEqual(lcp2.name, 'LCP');
assert.strictEqual(lcp2.value, lcp2.delta);
assert.strictEqual(lcp2.entries.length, 0);
assert.strictEqual(lcp2.navigationType, 'back_forward_cache');
await clearBeacons();
await stubForwardBack();
await beaconCountIs(1);
const [lcp3] = await getBeacons();
assert(lcp3.value > 0); // Greater than the image load delay.
assert(lcp3.id.match(/^v2-\d+-\d+$/));
assert.strictEqual(lcp3.name, 'LCP');
assert.strictEqual(lcp3.value, lcp3.delta);
assert.strictEqual(lcp3.entries.length, 0);
assert.strictEqual(lcp3.navigationType, 'back_forward_cache');
});
it('reports if the page is restored from bfcache even when the document was hidden at page load time', async function() {
if (!browserSupportsLCP) this.skip();
await browser.url('/test/lcp?hidden=1');
await stubVisibilityChange('visible');
// Click on the h1.
const h1 = await $('h1');
await h1.click();
// Wait a bit to ensure no beacons were sent.
await browser.pause(1000);
const beacons = await getBeacons();
assert.strictEqual(beacons.length, 0);
await stubForwardBack();
await beaconCountIs(1);
const [lcp2] = await getBeacons();
assert(lcp2.value > 0); // Greater than the image load delay.
assert(lcp2.id.match(/^v2-\d+-\d+$/));
assert.strictEqual(lcp2.name, 'LCP');
assert.strictEqual(lcp2.value, lcp2.delta);
assert.strictEqual(lcp2.entries.length, 0);
assert.strictEqual(lcp2.navigationType, 'back_forward_cache');
await clearBeacons();
await stubForwardBack();
await beaconCountIs(1);
const [lcp3] = await getBeacons();
assert(lcp3.value > 0); // Greater than the image load delay.
assert(lcp3.id.match(/^v2-\d+-\d+$/));
assert.strictEqual(lcp3.name, 'LCP');
assert.strictEqual(lcp3.value, lcp3.delta);
assert.strictEqual(lcp3.entries.length, 0);
assert.strictEqual(lcp3.navigationType, 'back_forward_cache');
});
});
const assertStandardReportsAreCorrect = (beacons) => {
const [lcp] = beacons;
assert(lcp.value > 500); // Greater than the image load delay.
assert(lcp.id.match(/^v2-\d+-\d+$/));
assert.strictEqual(lcp.name, 'LCP');
assert.strictEqual(lcp.value, lcp.delta);
assert.strictEqual(lcp.entries.length, 1);
assert.match(lcp.navigationType, /navigate|reload/);
};
const assertFullReportsAreCorrect = (beacons) => {
const [lcp1, lcp2] = beacons;
assert(lcp1.value < 500); // Less than the image load delay.
assert(lcp1.id.match(/^v2-\d+-\d+$/));
assert.strictEqual(lcp1.name, 'LCP');
assert.strictEqual(lcp1.value, lcp1.delta);
assert.strictEqual(lcp1.entries.length, 1);
assert.match(lcp1.navigationType, /navigate|reload/);
assert(lcp2.value > 500); // Greater than the image load delay.
assert.strictEqual(lcp2.value, lcp1.value + lcp2.delta);
assert.strictEqual(lcp2.name, 'LCP');
assert.strictEqual(lcp2.id, lcp1.id);
assert.strictEqual(lcp2.entries.length, 1);
assert(lcp2.entries[0].startTime > lcp1.entries[0].startTime);
assert.match(lcp2.navigationType, /navigate|reload/);
};