Run selenium in the host with docker and Capybara

Question

I have tests with capybara in a docker container. I use this to setup selenium :

Capybara.register_driver :selenium do |app|
  require 'selenium/webdriver'
  Selenium::WebDriver::Firefox::Binary.path = ENV['FIREFOX_BINARY_PATH'] || Selenium::WebDriver::Firefox::Binary.path
  Capybara::Selenium::Driver.new(app, :browser => :firefox)
end

It work when we run tests with xvfb but I want to see the real browser when tests are running so I'm looking for a way to use the browser in the host.

I think it's possible to launch geckodriver on the host and share the port 4444 but I didn't succeeded yet. Capybara launch a new instance of geckodriver, on the container, each time.

What can I do?

Edit 1 : Add more info

I all config I have for capybara :

#<Capybara::SessionConfig:0x0055ce67731a00
 @always_include_port=false,
 @app_host="http://domain-test.engagement.lvh.me:1300",
 @automatic_label_click=false,
 @automatic_reload=true,
 @default_host="http://www.example.com",
 @default_max_wait_time=5,
 @default_selector=:css,
 @enable_aria_label=false,
 @exact=false,
 @exact_text=false,
 @ignore_hidden_elements=true,
 @match=:smart,
 @raise_server_errors=true,
 @run_server=true,
 @save_path=#<Pathname:/app/tmp/capybara>,
 @server_errors=[StandardError],
 @server_host=nil,
 @server_port=1300,
 @visible_text_only=false,
 @wait_on_first_by_default=false>

Here is my docker-compose file :

version: '3'
services:
  web:
    build: .
    command: rails s -b 0.0.0.0
    working_dir: /app
    volumes:
      - .:/app
      - ./tmp/bundle:/usr/local/bundle
      - $SSH_AUTH_SOCK:/ssh-agent
    environment:
      - BUNDLE_JOBS=4
      - SSH_AUTH_SOCK=/ssh-agent
      - MONGO_HOST=mongo
      - REDIS_HOST=redis
      - MEMCACHE_HOST=memcache
    ports:
      - "80:3000"
      - "1300:1300"
    links:
      - mongo
      - redis
      - memcache

  mongo:
    image: mongo:3.4.9
    volumes:
      - ~/data/mongo/db:/data/db

  redis:
    image: redis:2.8.17
    volumes:
      - ~/data/redis:/data

  memcache:
    image: memcached:1.5-alpine

And finally my Dockerfile :

FROM ruby:2.3.1

RUN apt-get update && apt-get install -y build-essential qt5-default \
  libqt5webkit5-dev gstreamer1.0-plugins-base gstreamer1.0-tools gstreamer1.0-x \
  xvfb rsync

ARG GECKODRIVER_VERSION=0.19.0
RUN wget --no-verbose -O /tmp/geckodriver.tar.gz https://github.com/mozilla/geckodriver/releases/download/v$GECKODRIVER_VERSION/geckodriver-v$GECKODRIVER_VERSION-linux64.tar.gz \
  && rm -rf /opt/geckodriver \
  && tar -C /opt -zxf /tmp/geckodriver.tar.gz \
  && rm /tmp/geckodriver.tar.gz \
  && mv /opt/geckodriver /opt/geckodriver-$GECKODRIVER_VERSION \
  && chmod 755 /opt/geckodriver-$GECKODRIVER_VERSION \
  && ln -fs /opt/geckodriver-$GECKODRIVER_VERSION /usr/bin/geckodriver

RUN apt-get install -y libgtk-3-dev \
  && wget --no-verbose https://ftp.mozilla.org/pub/firefox/releases/56.0/linux-x86_64/en-US/firefox-56.0.tar.bz2 \
  && tar -xjf firefox-56.0.tar.bz2 \
  && mv firefox /opt/firefox56 \
  && ln -s /opt/firefox56/firefox /usr/bin/firefox

ENV TZ Europe/Paris
RUN echo $TZ > /etc/timezone && \
    apt-get update && apt-get install -y tzdata && \
    dpkg-reconfigure -f noninteractive tzdata && \
    apt-get clean

RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 0C49F3730359A14518585931BC711F9BA15703C6 && \
    echo "deb http://repo.mongodb.org/apt/debian jessie/mongodb-org/3.4 main" | tee /etc/apt/sources.list.d/mongodb-org-3.4.list && \
    apt-get update && \
    apt-get install -y mongodb-org

RUN gem install bundler

RUN mkdir /app
WORKDIR /app

the simplest thing would be to install the browser inside a docker and run the test on it. You could also install vnc client which will help you debug the tests. — Gaurang Shah
@GaurangShah VNC seems to be a little bit complicated for this simple thing. I'm sure there is a better solution. — Dougui
Selenium have pre built images, both standalone and hub versions. Then you get a port to connect to and don't have to bother with manage all the browser launching guff. — Matt
@Matt it seems I have the same problem I explained in the answer of Thomas Walpole. I have "Whoops! The URL specified routes to this help page." on each pae. — Dougui

Thomas Walpole Thomas Walpole · Accepted Answer · 2017-10-18T17:33:31

In order to get Selenium to use a remote geckodriver instance you need to provide the url option to it.

Capybara.register_driver :selenium do |app|
  require 'selenium/webdriver'
  Capybara::Selenium::Driver.new(app, :browser => :firefox, url: 'http://<your ip as reachable from docker>:<port geckodriver is available on>')
end

This will then require you to run geckodriver on the machine your want firefox to run on, possibly using the --binary option to specify where firefox is located. It will also probably require setting Capybara.app_host (and possibly Capybara.always_include_port depending on your exact configuration) so the browser requests are routed back to the app under test running on the docker instance.

Another thing to consider is that the AUT will need to be bound to an interface on the docker instance which is reachable from the host. By default Capybara binds to the 127.0.0.1 interface which probably isn't reachable, so you can set Capybara.server = '0.0.0.0' to bind to all available interfaces, or specify the specific external interface.

Run selenium in the host with docker and Capybara

Edit 1 : Add more info

1 Answers