If you are building an ESM module and you use the import format:

import { OpenAPIObject } from "openapi3-ts/src/model/openapi31";

and use mocha with:

{
  "loader": "ts-node/esm"
}

unit tests will fail.

The "fix" is to use the import format:

import { oas31 } from "openapi3-ts";

Since the second format works, I don't expect any code change here. I'm mainly creating this issue in case others run into the same problem.

It might be good to update the readme to note this.