Scalable Tests for Responsive Web: Running Cucumber and Capybara with Tags in Dockers

If you are using Capybara with Cucumber, tagging is a very efficient feature of the
Cucumber for manageable test cases. Tagging can be also used for managing test environments, like @test may mean that these tests run only in the test environment so set the environment as the test for me. Likely @live may mean that these tests can run on the live environment, assume that you are applying continuous testing. You can also give the scenarios for device-specific tags, like @ihphone6_v may say these tests are for iphone6 with the vertical mode.

Moreover, with tagging, you can also make an isolation strategy for running your test in parallel. Each parallel suits should have its own data like users, active records, address, credit card info, and ext. I have used the tagging for running tests in dockers. In this post, you can find some practical way of running Capybara with Cucumber in Dockers.

Creating Docker Image: Dockerfile

I am using Ruby version 2.3 so in Dockerfile getting the image of FROM Ruby:2.3 which is the first layer of the image comes as a Debian os. Then installing required libraries with the RUN command. Changing the working directory with WORKDIR which we will use this path by mounting the project folder into the running Docker. COPY Gemfile to WORKDIR so we can RUN bundle install to install required gems. The last thing, we need to install Chromedriver and Chrome by RUN commands. These steps executed by the Dockerfile, check it below:

Running Capybara in a Docker

Running the Capybara with my image is pretty simple if you run it without docker, just try other options which most suited for your case.

docker run --shm-size 256M --rm --name capybara_m \
 -v $PWD:/usr/src/app gunesmes/docker-capybara-chrome:latest bash \
 -c "cucumber features/G001_basket_product_checks.feature DRIVER=driver_desktop"

the meaning of the parameters in the command as follows:
  • run: running docker 
  • --shm-size: Size of /dev/shm. Shared memory size, if you do not set it Chromedriver may be unreachable if there is no allocated memory.
  • --rmAutomatically remove the container when it exits so we can rerun if fails
  • --name: Assign a name to the container
  • -v: Bind mount a volume, we are mounting the local files, inside the container.  $PWD:/usr/src/app means to mount the path present working directory to the path called /app inside the container
  • gunesmes/docker-capybara-chrome: name of the images which simulate the local machine works as Capybara machine. For the first time you run, it downloads the images from, but for the later run, it will just download the updated container layers if there are.
  • :latestversion of the image, if you tagged your image when building it, you can use it.
  •  . . .: and the rest of commands are for the Cucumber specific. You can see them in Cucumber docs.

Visual Run for iPhone6

For debugging purposes you may need to run the test visually to see if everything happens as expected. For this purpose set the visibility of the driver as visible by selecting the one in the list of env.rb file. Therefore the following command simply runs the test via iPhone 6, vertical mode visible. You can also see the video for this run.
cucumber features/G001_basket_product_checks.feature DRIVER=driver_mobile_iphone6_v_visible

Docker run for a single tag with a single platform

You can run a feature for a single platform by defining the DRIVER option with the desired one. In the following run command we can run one feature file for the driver running on the desktop.
docker run --shm-size 256M --rm --name capybara_m \
-v $PWD:/usr/src/app gunesmes/docker-capybara-chrome:latest bash \ -c "cucumber features/G001_basket_product_checks.feature DRIVER=driver_desktop"

Docker run for parallel execution of smoke test

check the reports inside the ./html_report

Docker run for parallel execution of all tags with all platforms


When we run the, there is only two parallel run executed against the desktop version of chrome and iPhone 6 version of chrome with the vertical mode. Mobile for better experiences we both set the dimension of the mobile devices and the user-agent for mobile device operating system. However, there is still a technical problem that we don't run the test in real devices. Check the browser object in the env.rb.  You can run the in a dedicated environment, it just requires more resources than an ordinary machine. 

In the end, it creates JSON report files in the ./report folder so that you can create nice HTML reports with cucumber-JVM report plugin for Jenkins. It includes screenshots on error and the logs of the browser. 

Check the result of the log, you can the benefit of the parallel run. Each test takes approximately 1 minute when we run the, there are 7 parallel runs but all test takes approximately 1minute 20seconds.


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