Function assertScreenshot

front_end/testing/DOMHelpers.ts:328–353

(filename: string)

 * The function relies on the bindings exposed via the karma config.
 */
export async function assertScreenshot(filename: string) {
  // To avoid a lot of empty space in the screenshot.
  document.getElementById(TEST_CONTAINER_ID)!.style.width = 'fit-content';
  let frame: Window|null = window;
  while (frame) {
    frame.scrollTo(0, 0);
    frame = frame.parent !== frame ? frame.parent : null;
  }

  // For test we load the fonts though the network - front_end/testing/test_setup.ts
  // Which means we may try to take screenshot while they are loading
  await document.fonts.ready;
  await raf();
  // Pending activity before taking screenshots results in flakiness.
  await checkForPendingActivity();
  if (!window.assertScreenshot) {
    window.assertScreenshot = async () => {
      debugger;  // eslint-disable-line no-debugger
      return undefined;
    };
  }
  const errorMessage = await window.assertScreenshot(`#${TEST_CONTAINER_ID}`, filename);
  if (errorMessage) {
    throw new Error(errorMessage);
  }
}

export function setColorScheme(scheme: 'dark'|'light'): void {
  document.documentElement.classList.toggle('theme-with-dark-background', scheme === 'dark');