Add admin page e2e test

tests/testcafe/admin.test.ts

@@ -0,0 +1,17 @@
+/**
+ * TestCafé test fixtures.
+ * This file is used by TestCafé to run end-to-end tests with chrome against the site.
+ * Tests are grouped into fixtures and fixtures into files.
+ */
+import { Selector } from "testcafe";
+
+fixture`Admin page renders and functions correctly`.page("http://localhost:3000/admin");
+
+test("Header contains text \"Admin panel\"", async t => {
+  /**
+   * Test if the header contains the text.
+   */
+  const header = Selector("h1");
+  await t.expect(header.textContent)
+         .contains("Admin panel");
+});