test: test urls fetching only if fetch is available

test/PDFMerger-browser.test.js

@@ -9,13 +9,6 @@ import { jest } from '@jest/globals'
 
 import PDFMerger from '../browser'
 
-/*
-  add a global `windows.fetch` to mock fetch
-*/
-global.window.fetch = jest.fn().mockImplementation((requestUrl) => {
-  return Promise.resolve(fetch(requestUrl))
-})
-
 const __dirname = path.dirname(new URL(import.meta.url).pathname)
 const FIXTURES_DIR = path.join(__dirname, 'fixtures')
 const TMP_DIR = path.join(__dirname, 'tmp')
@@ -175,7 +168,8 @@ describe('PDFMerger for browser', () => {
       expect(diff).toBeFalsy()
     })
 
-    test('merge pdfs from urls', async () => {
+    const testIfFetch = typeof fetch !== 'undefined' ? test : test.skip
+    testIfFetch('merge pdfs from urls', async () => {
       const merger = new PDFMerger()
 
       await merger.add(