TypeError: Unknown file extension ".ts" with Chai 5.0.0 and later

[npapagna]

I get TypeError: Unknown file extension ".ts" when trying to run mocha tests using ts-node with chai 5.0.0 and later. Downgrading it to 4.4.1 seems to fix the issue.

Check this repo with a minimal example that reproduces the bug

[43081j]

this is because chai 5.x is esm-only

if you're in a commonjs project, you should stick to 4.x (which we are still supporting) or migrate to ESM (add type: "module" to your package.json).

you can see an example of an esm project working with ts-node and mocha here: https://gist.github.com/43081j/78ce1392abb5043b02a29355006880a5/

[npapagna]

Thanks, it worked great!