chrome-devtools-frontend/front_end/models/trace/handlers/SelectorStatsHandler.test.ts

Chrome DevTools UI

// Copyright 2024 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import {TraceLoader} from '../../../testing/TraceLoader.js';
import * as Trace from '../trace.js';

describe('SelectorStatsHandler', () => {
  it('associates timings and stats with each UpdateLayoutEvent', async function() {
    Trace.Handlers.ModelHandlers.SelectorStats.reset();

    const events = await TraceLoader.rawEvents(this, 'selector-stats.json.gz');
    for (const event of events) {
      Trace.Handlers.ModelHandlers.SelectorStats.handleEvent(event);
    }
    const data = Trace.Handlers.ModelHandlers.SelectorStats.data();

    // There are 10 UpdateLayoutTree events that we expect to find
    // SelectorStats for.
    assert.strictEqual(data.dataForUpdateLayoutEvent.size, 10);

    // We need the first updateLayoutEvent that happened before the
    // SelectorStats. This timestamp was found by looking through the trace and
    // finding the first SelectorStats event, and then finding the closest
    // previous UpdateLayoutTreeEvent
    const targetTimeStamp = 400015719531;
    const updateLayoutEvent = events.find(event => {
      return Trace.Types.Events.isUpdateLayoutTree(event) && event.ts === targetTimeStamp;
    });
    assert.isOk(updateLayoutEvent);

    if (!Trace.Types.Events.isUpdateLayoutTree(updateLayoutEvent)) {
      assert.fail('Event was of the wrong type.');
    }

    const selectorInfo = data.dataForUpdateLayoutEvent.get(updateLayoutEvent);
    assert.isOk(selectorInfo);
    // Ensure that we dumped the timings into the event
    assert.lengthOf(selectorInfo.timings, 325);
  });
});