https://www.npmjs.com/package/@typescript/vfs

TypeScript VFS
A Map based TypeScript Virtual File System.
Useful when you need to:

• Run TypeScript in the browser
• Run virtual TypeScript environments where files on disk aren't the source of truth

We have a lot of fixture files across our suite - some of which are used in a single test, some of which are shared across many tests.

In both cases, it can be a bit hard to reason about what's used where and what to do when you need a new fixture.

In one test suite, the test even makes use of temporary files to do its testing.

Setting up a VFS was always tempting to do, but too much overhead to setup and maintain.
Now with an official typescript maintained VFS, that bar is much lower.

A VFS could make the tests more isolated, and thus easier to understand, create and modify.