How to overcome test file caching for karma and webpack?

Question

caching

There is karma.conf.js https://github.com/Ineigo/karma-es6-webpack-config... if you run it like this: karma start karma.config.js --auto-watch --no-single- run. Then when changing the test files (spec), karma runs the cached files and shows the wrong result. I found a lot of issue about this, but I did not find a solution for myself. Who is dealing with this?