Creating a FixedLengthStream

[bstopp]

Probably a very basic question, but how do you create an instance of FixedLengthStream ?

Created a new project via npx create-cloudflare@latest and just adding a simple line of:

const fls = new FixedLengthStream(8);

Doesn't throw an error when i run the tests - but that type isn't defined.

However, when I add the same logic to my live project, I get FixedLengthStream is not defined.

Is the test only working because the demo Hello World project uses vitest? Is there any way to make this work using Miniflare?(what I'm using in my project)

Any help would be appreciated.