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

src/pages/LoginPage.test.jsx

@@ -3,6 +3,7 @@ import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
 import {cleanup, fireEvent, render, screen, waitFor} from '@testing-library/react';
 import {MemoryRouter, Route, Routes, useLocation} from 'react-router-dom';
 import LoginPage from './LoginPage.jsx';
+import {fetchRoutes, json} from '../test/fetchRoutes.js';
 
 vi.mock('react-i18next', () => import('../test/i18n-mock.js'));
 
@@ -22,6 +23,9 @@ function renderLogin(state) {
     );
 }
 
+// The page reads Retry-After from a refusal.
+const refused = (status, code) => ({...json(status, {code}), headers: new Headers()});
+
 function submit() {
     fireEvent.change(screen.getByLabelText('LOGIN.EMAIL'), {target: {value: 'a@b.de'}});
     fireEvent.change(screen.getByLabelText('LOGIN.PASSWORD'), {target: {value: 'secret'}});
@@ -30,7 +34,7 @@ function submit() {
 
 describe('LoginPage', () => {
     beforeEach(() => {
-        globalThis.fetch = vi.fn(async () => ({ok: true, status: 200, json: async () => ({message: 'Login successful'})}));
+        fetchRoutes({'POST /api/auth/login': json(200, {message: 'Login successful'})});
     });
 
     afterEach(() => {
@@ -72,7 +76,7 @@ describe('LoginPage', () => {
     });
 
     it('hides the expired message once a login attempt fails', async () => {
-        fetch.mockResolvedValueOnce({ok: false, status: 401, headers: new Headers(), json: async () => ({code: 'INVALID_CREDENTIALS'})});
+        fetchRoutes({'POST /api/auth/login': refused(401, 'INVALID_CREDENTIALS')});
         renderLogin({sessionExpired: true, from: '/library'});
 
         submit();
@@ -82,7 +86,7 @@ describe('LoginPage', () => {
     });
 
     it('says that a blocked account is blocked', async () => {
-        fetch.mockResolvedValueOnce({ok: false, status: 403, headers: new Headers(), json: async () => ({code: 'ACCOUNT_BLOCKED'})});
+        fetchRoutes({'POST /api/auth/login': refused(403, 'ACCOUNT_BLOCKED')});
         renderLogin();
 
         submit();