refactor: add shared fixtures and test.step() patterns

- Add tests/e2e/lib/fixtures.ts with shared test helpers
- Add tests/e2e/fixtures/diagrams.ts with XML test data
- Add expectBeforeAndAfterReload() helper for persistence tests
- Add test.step() for better test reporting in complex tests
- Consolidate mock helpers into fixtures module
- Reduce code duplication across 17 test files

tests/e2e/smoke.spec.ts

@@ -1,4 +1,4 @@
-import { expect, test } from "@playwright/test"
+import { expect, getIframe, openSettings, test } from "./lib/fixtures"
 
 test.describe("Smoke Tests", () => {
     test("homepage loads without errors", async ({ page }) => {
@@ -8,8 +8,7 @@ test.describe("Smoke Tests", () => {
         await page.goto("/", { waitUntil: "networkidle" })
         await expect(page).toHaveTitle(/Draw\.io/i, { timeout: 10000 })
 
-        // Wait for draw.io iframe to be present
-        const iframe = page.locator("iframe")
+        const iframe = getIframe(page)
         await expect(iframe).toBeVisible({ timeout: 30000 })
 
         expect(errors).toEqual([])
@@ -22,7 +21,7 @@ test.describe("Smoke Tests", () => {
         await page.goto("/ja", { waitUntil: "networkidle" })
         await expect(page).toHaveTitle(/Draw\.io/i, { timeout: 10000 })
 
-        const iframe = page.locator("iframe")
+        const iframe = getIframe(page)
         await expect(iframe).toBeVisible({ timeout: 30000 })
 
         expect(errors).toEqual([])
@@ -30,20 +29,8 @@ test.describe("Smoke Tests", () => {
 
     test("settings dialog opens", async ({ page }) => {
         await page.goto("/", { waitUntil: "networkidle" })
+        await getIframe(page).waitFor({ state: "visible", timeout: 30000 })
 
-        // Wait for page to load
-        await page
-            .locator("iframe")
-            .waitFor({ state: "visible", timeout: 30000 })
-
-        // Click settings button (gear icon)
-        const settingsButton = page.locator('[data-testid="settings-button"]')
-        await expect(settingsButton).toBeVisible()
-        await settingsButton.click()
-
-        // Check if settings dialog appears
-        await expect(page.locator('[role="dialog"]')).toBeVisible({
-            timeout: 5000,
-        })
+        await openSettings(page)
     })
 })