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Selenium Cucumber Docker

This repo provides a simple way to setup a Ruby/Cucumber/Capybara/Selenium based environment for test automation with Behaviour Driven Development (BDD).

Check out the related blog post & video.

History

Feb 2023 - updated to use Selenium 4

Quick start (tl;dr)

Open a terminal in root directory and follow these steps:

# Use docker compose to start start the two services
# and open a bash session in the 'ruby' service:

docker-compose run ruby bash
# Note: This could take a few min the first time you run...

# To see inside the browser, just open http://localhost:7900/?autoconnect=1&resize=scale&password=secret

# Back in the original terminal session, we're now inside our ruby service.
# Run the tests with cucumber
cucumber

# When you're done, you can exit the ruby container
exit

# Now (from the host machine) stop all the containers
docker-compose down

Background

The basic components of BDD are:

  • A running application to test (usually a web app)
  • A web browser (like Chrome or firefox) to render the app and give access to the UI elements
  • A web driver (like Selenium) to drive the browser
  • A testing framework (like Capybara) to examine (and interact with) elements on the page
  • A BDD framework (like Cucumber) to describe our tests (using Gherkin syntax), run them for us, and report on the results.
  • Some language to define the step definitions and tie everything together (in this case, Ruby)

Using Docker

Docker compose makes it easy to package all the components into a couple of simple services (containers) and mount your source code into the containers from the host, without installing anything locally.

  • The first service (which we'll call 'ruby') will hold the ruby runtime and any gems we need (e.g. cucumber and capybara). We'll build this with our Dockerfile.
  • The second service (which we'll call 'browser') will be an instance of the stand-alone Selenium-Chrome container.
  • NOTE: for Apple silicon (e.g. the M1 chip) you'll need to use the special M1 "seleniarm" ports.

Seeing the browser

You can easily open open a browser tab with a VNC client into the running container via this link

TROUBLESHOOTING

Getting an error that port 5900 is already allocated.

You may have "Screen sharing" enabled on your mac. Go to "Settings" > "Sharing" and untick the "Screen Sharing box"

Advanced usage

Run tests in one step

docker-compose run ruby cucumber

Using the 'pry' debugger.

You can add a step And I debug to your features to open the pry interactive debugger which lets you write code to interact with the browser in real-time without restarting your tests.

Use Scenario Outlines

You can use "scenario outlines" to quickly run through the same scenario with different variables.