DOCKER TUTORIAL

VM vs Containers:
Definitions:

Docker Container can be created by docker image.

Docker Hub:
Docker in Automation:

Docker Terminology:
Docker Commands:

Docker run -it image_name – to create container from image

Docker system prune -f – Delete all inactive containers

Docker kill container_name – Kill a containers

Docker run example:

Project Structure Example

cpp

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my-selenium-project/

├── tests/

│ └── test_example.py
├── requirements.txt

├── Dockerfile

└── pytest.ini (optional)

📄 requirements.txt

Include all dependencies:

txt

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selenium

pytest

You may also want to add:

txt

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pytest-html

webdriver-manager

🐳 Dockerfile

This sets up Python with Selenium and runs Pytest:

Dockerfile

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# Use official Python image

FROM python:3.11-slim

# Install dependencies for Selenium (e.g., Chrome & driver)

RUN apt-get update && apt-get install -y \

wget \

curl \

unzip \

chromium-driver \
 chromium \

&& apt-get clean

# Set environment variables to use Chromium

ENV CHROME_BIN=/usr/bin/chromium

ENV PATH="$PATH:/usr/bin/chromium"

# Set workdir

WORKDIR /app

# Copy project files

COPY . .

# Install Python dependencies

RUN pip install --no-cache-dir -r requirements.txt

# Default command to run tests

CMD ["pytest", "--maxfail=1", "--disable-warnings", "-v"]

🧪 Example Test: tests/test_example.py

python

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from selenium import webdriver

from selenium.webdriver.chrome.options import Options

def test_google_search():

options = Options()

options.add_argument('--headless')

options.add_argument('--no-sandbox')
 options.add_argument('--disable-dev-shm-usage')

driver = webdriver.Chrome(options=options)

driver.get("https://www.google.com")

assert "Google" in driver.title

driver.quit()

Build and Run the Container

bash

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# Build the image

docker build -t selenium-tests .

# Run the container

docker run --rm selenium-tests

📝 Notes

 This runs tests in headless Chromium.

 Add pytest-html if you want an HTML report.

 For Firefox instead of Chrome, change the Dockerfile to install firefox

How to run locally and with selenium grid:

1. docker-compose.yml for Local Testing (Headless Chrome)

This setup:

Uses a single container.

Runs Selenium + Pytest with Chromium in headless mode.

cpp

Copy

Edit

my-selenium-project/

├── tests/

│ └── test_example.py

├── requirements.txt

├── Dockerfile

├── docker-compose.yml

└── pytest.ini (optional)

📄 Dockerfile

(Use the same one from earlier, see above)

📄 docker-compose.yml

yaml

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Edit

version: '3.8'

services:

test-runner:

build: .

container_name: selenium_pytest

volumes:

- .:/app

working_dir: /app

▶️Run the Tests

bash
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docker-compose up --build

✅ 2. Selenium Grid Setup with Chrome/Firefox Nodes

This is a more advanced setup for full browser support, useful for parallel
tests and debugging.

🔧 Project Files

css

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Edit

my-selenium-grid-project/

├── tests/

│ └── test_example.py

├── requirements.txt

├── docker-compose.yml

└── Dockerfile

📄 Dockerfile (Pytest + Selenium only)

Dockerfile

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FROM python:3.11-slim

WORKDIR /tests

COPY requirements.txt .

RUN pip install --no-cache-dir -r requirements.txt

COPY tests/ ./tests/

📄 docker-compose.yml

yaml

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version: '3.8'

services:

selenium-hub:

image: selenium/hub:4.18.1

container_name: selenium-hub

ports:

- "4444:4444"

chrome:

image: selenium/node-chrome:4.18.1

depends_on:

- selenium-hub

environment:

- SE_EVENT_BUS_HOST=selenium-hub

- SE_EVENT_BUS_PUBLISH_PORT=4442

- SE_EVENT_BUS_SUBSCRIBE_PORT=4443

firefox:

image: selenium/node-firefox:4.18.1

depends_on:

- selenium-hub

environment:
 - SE_EVENT_BUS_HOST=selenium-hub

- SE_EVENT_BUS_PUBLISH_PORT=4442

- SE_EVENT_BUS_SUBSCRIBE_PORT=4443

test-runner:

build: .

depends_on:

- selenium-hub

volumes:

- ./tests:/tests

🧪 Example: test_example.py

python

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Edit

from selenium import webdriver

from selenium.webdriver.common.by import By

from selenium.webdriver.chrome.options import Options

def test_google_grid():

options = Options()

options.add_argument("--headless")

driver = webdriver.Remote(

command_executor='http://selenium-hub:4444/wd/hub',

options=options

driver.get("https://www.google.com")

assert "Google" in driver.title

driver.quit()

▶️Run All with:

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docker-compose up –build

What is the Difference Between Docker stop and Docker