Inline Svelte components for tests

Describe the problem

I'll start off by saying I don't know whether this would be a Svelte feature, or maybe part of a Vite plugin, or even if this should be in another library.

When I'm writing component tests using something like testing-library, I'll need to write some code like this (which requires jumping from file to file):

import {render} from '@testing-library/svelte'
import MyComponent from './MyComponent.svelte'

const result = render(MyComponent, componentOptions, renderOptions)

This leaves me jealous of frameworks like React where you can inline JSX and see a lot more of your component code (all of it, if you really wanted to):

import {render, screen} from '@testing-library/react'
import Fetch from './fetch'

test('loads and displays greeting', async () => {
  render(<Fetch url="/greeting" />)

I'm attempting to port Tailwind's HeadlessUI-React library to Svelte 5, and in the process of porting, there are hundreds (thousands?) of inline JSX examples to test components in different ways, eg:

https://github.com/tailwindlabs/headlessui/blob/main/packages/%40headlessui-react/src/components/switch/switch.test.tsx

it('should be possible to render an (on) Switch using a render prop', () => {
  render(
    <Switch checked={true} onChange={console.log}>
      {({ checked }) => <span>{checked ? 'On' : 'Off'}</span>}
    </Switch>
  )
  ...

Writing a custom Svelte file per test would be annoying, but moreso, just trying to debug that becomes a nightmare very quickly (I know, I've tried).

Describe the proposed solution

I have a partial solution that I'm kinda meh about, but think this might be a better first-party plugin or solution. Or maybe I can directly use the compiler or createRawSnippet to facilitate this, but I honestly am not sure about any of that.

Using a hacked together Vite plugin, I - on-the-fly - compile Svelte template strings into virtual modules, and