npm install mock-fsyarn add mock-fspnpm add mock-fs<script src="https://fastly.jsdelivr.net/npm/mock-fs"></script><script src="https://unpkg.com/mock-fs"></script><script type="module">
import mockfs from 'https://cdn.jsdelivr.net/npm/mock-fs/+esm';
</script><script type="module">
import mockfs from 'https://cdn.skypack.dev/mock-fs';
</script>