To automate browsers you need one or more of these ports:
www/firefox
www/chromium

With one or more of these complementary ports:
www/geckodriver
x11-servers/xorg-vfbserver
x11-fonts/xorg-fonts
x11-fonts/webfonts
x11/xauth
x11/xkeyboard-config
x11/xkbcomp

Clients can also be found:
www/rubygem-selenium-webdriver
www/py-selenium
devel/p5-Test-WWW-Selenium