Run npm install && npx mocha test.ts. You'll get an error like Exception during run: Error [ERR_INTERNAL_ASSERTION]: Unexpected status of a module that is imported again after being required. Status = 0. This is caused by mochajs/mocha#5411, which was already fixed. But using the 11.7.2 version of mocha still results in an error, just with a better message: Exception during run: SyntaxError: The requested module './foo.js' does not provide an export named 'Foo'.