add e2e tests for 404 pages

ui-e2e-tests/page-not-found.spec.ts

@@ -0,0 +1,20 @@
+import { test, expect, type Page } from '@playwright/test'
+
+async function test404Page(page: Page, url: string) {
+	const response = await page.goto(url)
+	expect(response?.status()).toEqual(404)
+	const NotFoundTextLocator = page.getByText("The page you are looking for isn't here.")
+	await expect(NotFoundTextLocator).toBeVisible()
+}
+
+test('Trying to access a non existent page should result in a 404 page', async ({ page }) => {
+	await test404Page(page, 'http://127.0.0.1:8788/gibberish_fytr75235dfhhlplo')
+})
+
+test('Trying to access a non existent sub-page should result in a 404 page', async ({ page }) => {
+	await test404Page(page, 'http://127.0.0.1:8788/explore/gibberish_fytr75235dfhhlplo')
+})
+
+test('Trying to access a non existent sub-sub-page should result in a 404 page', async ({ page }) => {
+	await test404Page(page, 'http://127.0.0.1:8788/explore/gibberish/fytr75235dfhhlplo')
+})