How to Run Selenium in Xvfb: Overcoming the 'Cannot Open Display' Error

Xvfb (X Virtual Framebuffer) provides a virtual display that enables the execution of graphical applications in headless environments, such as EC2 instances that lack a GUI. This is essential for running Selenium tests on servers without a graphical user interface.

However, even after installing Selenium and Xvfb, you may encounter the "Error: cannot open display: :0" when attempting to run tests. This stems from Selenium's reliance on a graphical display to interact with web pages.

Solution: Utilize PyVirtualDisplay or Xvfbwrapper

To resolve this issue, you can use PyVirtualDisplay or Xvfbwrapper, which encapsulate Xvfb as Python modules. These modules simulate a virtual display, allowing Selenium to run in headless environments:

Option 1: PyVirtualDisplay

from pyvirtualdisplay import Display
from selenium import webdriver

display = Display(visible=0, size=(800, 600))
display.start()

browser = webdriver.Firefox()
browser.get('http://www.google.com')
print(browser.title)
browser.quit()

display.stop()

Option 2: Xvfbwrapper

from xvfbwrapper import Xvfb

vdisplay = Xvfb()
vdisplay.start()

browser = webdriver.Firefox()
browser.get('http://www.google.com')
print(browser.title)
browser.quit()

vdisplay.stop()

You can also utilize a context manager to simplify the process:

from xvfbwrapper import Xvfb

with Xvfb() as xvfb:
    # Launch stuff inside virtual display here.
    # It starts/stops in this code block.

By utilizing these modules, you can effectively run Selenium tests on headless servers that lack a graphical user interface, ensuring that your tests can execute successfully in any environment.