title: Run py.test in a docker container as a service
body: <p>I am working on setting up a dockerised selenium grid. I can send my python tests [run with pytest] from a pytest container [see below] by attaching to it.
  But I have setup another LAMP container that is going to control pytest.
  So I want to make the pytest container standalone,running idle and waiting for commands from the LAMP container.</p>
  
  <p>I have this Dockerfile:</p>
  
  <pre><code># Starting from base image
  FROM ubuntu
  
  #-----------------------------------------------------
  # Set the Github personal token
  ENV GH_TOKEN blablabla
  
  # Install Python &amp; pip
  RUN apt-get update
  RUN apt-get upgrade -y
  RUN apt-get install -y python python-pip python-dev &amp;&amp; pip install --upgrade pip
  
  # Install nano for #debugging
  RUN apt-get install -y nano
  
  # Install xvfb
  RUN apt-get install -y xvfb
  
  # Install GIT
  RUN apt-get update -y &amp;&amp; apt-get install git -y
  
  # [in the / folder] 
  RUN git clone https://$GH_TOKEN:x-oauth-basic@github.com/user/project.git /project
  
  # Install dependencies via pip
  WORKDIR /project
  RUN pip install -r dependencies.txt
  #-----------------------------------------------------
  
  #
  CMD ["/bin/bash"]
  </code></pre>
  
  <p>I start the pytest container manually [for development] with this:</p>
  
  <pre><code>docker run -dit -v /project --name pytest repo/user:py
  </code></pre>
  
  <p>The thing is that I finished development and I want to have the pytest container launched from <code>docker-compose</code> and connect it to other containers [with link and volume].
  I just cannot make it to stay up .</p>
  
  <p>I used this :</p>
  
  <pre><code>pytest:
    image: repo/user:py
    volumes:
      - "/project"
    command: "/bin/bash tail -f /dev/null"
  </code></pre>
  
  <p>but didnt work.</p>
  
  <p>So, inside the Dockerfile, should I use a specific CMD or ENTRYPOINT ?</p>
  
  <p>Should I use some <code>command</code> from the <code>docker-compose</code> file?</p>