example .gitlab-ci.yml

image: docker:18

services:
  - docker:dind

stages:
  - default
  - test
  - deploy

default:
  before_script:
    - docker login -u ${DOCKER_USER} -p ${DOCKER_PASSWORD}
    - docker build -t simpleapp .

test:
  stage: test
  script:
    - docker run -p 5000:5000 -d --name simpleapp simpleapp
    - docker ps | grep -q simpleapp

deploy:
  stage: deploy 
  script:
    - docker tag simpleapp howtoautomateinth/simpleapp-gitlab
    - docker push howtoautomateinth/simpleapp-gitlab