$driver = clone $this->mink->getSession()->getDriver();
$driver->reset();
$this->mink->registerSession('new', new Session($driver));
$this->mink->setDefaultSessionName('new');
// Do things.
// Switch back to the original.
$this->mink->setDefaultSessionName('default');
Well, it didn't switch back, my passing test became a failing one. As you can see the session name originally was default
. (This is not Drupal specific at all so it doesn't really belong on drupal SE.)
Don't use $this->mink->getSession()->getDriver()
Use new driver with:
$session = new Session(new GoutteDriver());
$this->getMink()->registerSession('new', $session);