To run it, you will need a binary distribution of PhantomJS-CEF.
There are several options for you. Please have a look at the PhantomJS-CEF's github page (https://github.com/aknuth/phantomjs-cef)
The test cases are actually just examples.
If you decide to use native binaries, you can start the test case using the System Parameter 'phantomjsDir' of the PhantomJS-CEF execution directory.
e.g. -DphantomjsDir=/home/aknuth/phantomjs-cef
If you are running the docker way, then should start the test case - the websocket server will be started - then do the docker call:
e.g. docker run -t -i --rm aknuth/phantomcef ./phantomjava.sh
this runs the phantomjs-cef binaray and thus the websocket client
You should get a lot of logging output ...
Have fun