CasperJS

CasperJS is built on top of PhantomJS, which means that your Casper environment is actually a PhantomJS environment with some extras. In your CasperJS script, you are using the tester module of CasperJS. But we can access the phantom object from there.
casper.test.setUp(function () {
  console.log('PhantomJS version: ' + phantom.version.major + '.' + phantom.version.minor + '.' + phantom.version.patch);
});