Running unit tests for front-end web applications require them to be tested in a web browser. While it's not an issue on a workstation, it can become tedious when running in a restricted environment such as a Docker container. In fact, these execution environments are generally lightweight and do not contain any graphical environment.
One solution to work around this issue is to use a headless web browser designed for development purposes, like PhantomJS. While it's an elegant solution for testing an application, it would be even better to test it directly in a web browser which will be used by the end-users in order to match real conditions of use, for examples Firefox or Chromium/Google Chrome. However, as mentioned above, it is needed to find a way to execute a regular web browser in a restricted environment.