PhantomJS can open local files without any problems. The url have to follow classic Url/Uri rules, especially for a local file.
/Full/Path/To/test.html
is not valid for PhantomJS. Is it a local file or a web resource?
Depending of the path, just try with something like this:
file:///C:/Full/Path/To/test.html
or if it’s hosted in a web server:
http://localhost/Full/Path/To/test.html