Function installVTMock

test/commands/viewTransition.js:8–29

* Install a minimal document.startViewTransition mock. `window.__vtLog` records * lifecycle events (start, skipped, finished) so tests can assert escape-path * behavior on the view transition itself rather than the surrounding DOM.

(evaluate)

 * behavior on the view transition itself rather than the surrounding DOM.
 */
async function installVTMock(evaluate) {
	await evaluate(() => {
		window.__vtLog = []
		document.startViewTransition = function (arg) {
			window.__vtLog.push('start')
			var skipped = false
			var updateFn = typeof arg === 'function' ? arg : arg.update
			var updateP
			try { updateP = updateFn() } catch (e) { updateP = Promise.reject(e) }
			var finished = Promise.resolve(updateP).then(
				function () { window.__vtLog.push('finished'); },
				function () { window.__vtLog.push('finished-err'); }
			)
			return {
				finished: finished,
				updateCallbackDone: Promise.resolve(updateP),
				ready: Promise.resolve(),
				skipTransition: function () { skipped = true; window.__vtLog.push('skipped') },
			}
		}
	})
}

test.describe("the start view transition command", () => {