Recreate 1711 problem
$ npm test
> [email protected] pretest /home/carlerik/dev/sinon-1711-babel
> npm run build
> [email protected] build /home/carlerik/dev/sinon-1711-babel
> babel src -d ./build
src/mod1.js -> build/mod1.js
src/mod1.spec.js -> build/mod1.spec.js
> [email protected] test /home/carlerik/dev/sinon-1711-babel
> mocha build
sinon#stub
✓ should correctly mock the module's method
1 passing (9ms)