test: data router, one render helper, fetchRoutes in every test

src/context/PreferencesContext.test.jsx

@@ -2,6 +2,7 @@
 import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
 import {act, cleanup, render} from '@testing-library/react';
 import {PreferencesProvider, usePreferences} from './PreferencesContext.jsx';
+import {fetchRoutes, json} from '../test/fetchRoutes.js';
 
 const i18n = vi.hoisted(() => ({language: 'de'}));
 vi.mock('react-i18next', async () => {
@@ -31,11 +32,10 @@ afterEach(() => {
     localStorage.clear();
 });
 
-const answerMe = (settings) => {
-    globalThis.fetch = vi.fn(async (url, init) => (init?.method === 'PUT'
-        ? {ok: true, status: 204}
-        : {ok: true, status: 200, json: async () => ({displayName: 'Lobo', settings})}));
-};
+const answerMe = (settings) => fetchRoutes({
+    'GET /api/users/me': json(200, {displayName: 'Lobo', settings}),
+    'PUT /api/users/settings': json(204),
+});
 
 describe('PreferencesProvider language', () => {
     it('takes the language saved in Auth', async () => {