createPage example

protected function setUp(): void
    {
        parent::setUp();

        $contextFactory = $this->getContainer()->get(SalesChannelContextFactory::class);

        $this->systemConfigService = $this->getContainer()->get(SystemConfigService::class);
        $this->systemConfigRepository = $this->getContainer()->get('system_config.repository');
        $this->cmsPageRepository = $this->getContainer()->get('cms_page.repository');
        $this->salesChannelContext = $contextFactory->create(Uuid::randomHex(), TestDefaults::SALES_CHANNEL);

        $this->errorLayoutId = $this->createPage();
        $this->systemConfigService->set('core.basicInformation.http404Page', $this->errorLayoutId);
    }

    public function testItDoesLoad404CmsLayoutPageIn404Case(): void
    {
        $request = new Request();
        $context = $this->createSalesChannelContextWithNavigation();

        /** @var ErrorPageLoadedEvent $event */
        $event = null;
        $this->catchEvent(ErrorPageLoadedEvent::class, $event);