This https://github.com/orta/vscode-jest/pull/25 wasn't quite right in the end, I need to run npm run jest -- --watch from the root of the jest repo in order to ensure the build transformations work right. So ideally, I'd be able to say "if I open at this folder, use this as cwd for jest".
is this the reason I'm getting Exception raised: Process failed: spawn node_modules\.bin\jest.cmd ENOENT?
Nah, I don't think so, do those files exist for you? what is the path to your Jest script
"test": "jest --coverage",

can you try setting your jest.pathToJest for this project to be npm test --?
where do I set this up?
in your project settings .vscode/settings.json
Exception raised: Process failed: spawn npm ENOENT
@luisrudge would recommend cloning this extension and having a look at what's going on
Closing, this isn't really the fix I was looking for.
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Exception raised: Process failed: spawn npm ENOENT