laravel mix mocha error

when i try to run mocha using laravel mix it gives me this error

Conflict: Multiple assets emit to the same filename bundle.js

how can i fix this with laravel mix ?

this is the command i am running

mocha-webpack --webpack-config=node_modules/laravel-mix/setup  /webpack.config.js --require tests/Javascript/setup.js tests/Javascript/*/.spec.js