With Docker you can quickly and easily install, configure and use Selenium Grid. This tutorial shows the respective steps that you need as a software tester (or Developer). Instead of Python you can also use other languages, which are supported by Selenium​.

Preconditions

• Python installed (min. 2.7)
• virtualenv installed (optional)
• docker-machine installed
• docker-compose installed

Preparation of files

# create new project
$ mkdir -p ~/Project/SeleniumTutorial && cd ~/Project/SeleniumTutorial

# create docker-compose.yml (version 1)
$ vim v1-docker-compose.yml

# or create docker-compose.yml (version 2)
$ vim v2-docker-compose.yml

# create python example.py
$ vim example.py

Note: You can opt for a version of docker-compose.yml!

Version: 1

---
selenium_hub:
  image: selenium/hub
  ports:
    - 4444:4444
node_1:
  image: selenium/node-chrome
  links:
    - selenium_hub:hub
node_2:
  image: selenium/node-firefox
  links:
    - selenium_hub:hub

Version: 2

---
version: '2'
services:
  selenium_hub:
    image: selenium/hub
    ports:
      - 4444:4444
  node_1:
    image: selenium/node-chrome
    depends_on:
      - selenium_hub
    environment:
      - HUB_PORT_4444_TCP_ADDR=selenium_hub
  node_2:
    image: selenium/node-firefox
    environment:
      - HUB_PORT_4444_TCP_ADDR=selenium_hub
    depends_on:
      - selenium_hub

import os
import datetime
import time
import unittest
from selenium import webdriver


class Example(unittest.TestCase):

    def setUp(self):

        self.driver = webdriver.Remote(
            command_executor='http://192.168.99.100:4444/wd/hub',
            desired_capabilities={
                'browserName': 'firefox',
                'javascriptEnabled': True
            }
        )

        self.driver.get('http://softwaretester.info/')

    def test_something(self):

        dt_format = '%Y%m%d_%H%M%S'
        cdt = datetime.datetime.fromtimestamp(time.time()).strftime(dt_format)
        current_location = os.getcwd()
        img_folder = current_location + '/images/'

        if not os.path.exists(img_folder):
            os.mkdir(img_folder)

        picture = img_folder + cdt + '.png'
        self.driver.save_screenshot(picture)

    def tearDown(self):

        self.driver.quit()


if __name__ == "__main__":

    unittest.main(verbosity=1)

Create environment

# create new VM
$ docker-machine create -d virtualbox Grid

# pointing shell
$ eval $(docker-machine env Grid)

# show status (optional)
$ docker-machine ls
...
NAME   ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER    ERRORS
Grid   *        virtualbox   Running   tcp://192.168.99.100:2376           v1.11.1 

# run docker-compose (Version: 1)
$ docker-compose -f v1-docker-compose.yml up -d

# run docker-compose (Version: 2)
$ docker-compose -f v2-docker-compose.yml up -d

# show status (Version: 1)
$ docker-compose -f v1-docker-compose.yml ps
...
             Name                         Command           State           Ports          
------------------------------------------------------------------------------------------
seleniumtutorial_node_1_1         /opt/bin/entry_point.sh   Up                           
seleniumtutorial_node_2_1         /opt/bin/entry_point.sh   Up                           
seleniumtutorial_selenium_hub_1   /opt/bin/entry_point.sh   Up      0.0.0.0:4444->4444/tcp

# show status (Version: 2)
$ docker-compose -f v2-docker-compose.yml ps
...
             Name                         Command           State           Ports          
------------------------------------------------------------------------------------------
seleniumtutorial_node_1_1         /opt/bin/entry_point.sh   Up                           
seleniumtutorial_node_2_1         /opt/bin/entry_point.sh   Up                           
seleniumtutorial_selenium_hub_1   /opt/bin/entry_point.sh   Up      0.0.0.0:4444->4444/tcp

Open Browser

Run Python script

# run python selenium script
$ python -B ~/Projects/Selenium/example.py

Note: Via browserName (example.py) you can choose the respective browser (firefox or chrome)!

Note: Via docker-compose scale you can add/remove node instances!

# create 2 instances (Version: 1)
$ docker-compose -f v1-docker-compose.yml scale node_1=2

# create 3 instances (Version: 2)
$ docker-compose -f v2-docker-compose.yml scale node_2=3