🧪 Add legacy token conversion test

apps/web/tests/legacy-token.spec.ts

@@ -0,0 +1,32 @@
+import test, { expect } from "@playwright/test";
+import { sealData } from "iron-session";
+
+/**
+ * This test checks that a legacy token can be used to sign in.
+ */
+test("should convert guest legacy token", async ({ browser }) => {
+  const context = await browser.newContext();
+  const guestLegacyToken = await sealData(
+    {
+      user: {
+        id: "user-1234",
+        isGuest: true,
+      },
+    },
+    {
+      password: process.env.SECRET_PASSWORD,
+    },
+  );
+  await context.addCookies([
+    {
+      name: "rallly-session",
+      value: guestLegacyToken,
+      httpOnly: true,
+      url: process.env.NEXT_PUBLIC_BASE_URL,
+    },
+  ]);
+  const page = await context.newPage();
+  await page.goto("/polls");
+  await page.getByTestId("user-dropdown").click();
+  await expect(page.locator("text=user-1234")).toBeVisible();
+});