Stop Being Lazy and Test Your Software
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DockerCon EU 2015 in Barcelona Practical tips for using Docker to run tests during development, CI/CD, and different strategies for speeding up the run of your test suite by using parallel pipelines in containers. The jet tool used to demonstrate parallel testing is available here: https://codeship.com/documentation/docker/installation/
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Stop Being Lazy and Test Your Software
- 1. Stop Being Lazy and Test Your Software! Laura Frank Software Engineer, Codeship
- 3. Agenda Continuous Delivery Why Do We Test? Testing with Docker Compose Faster Testing with Docker
- 4. Why Do We Test? Motivations and frustrations
- 5. Testing software has been a practice since the very first machines were used for computing.
- 7. The women who programmed the ENIAC to calculate trajectories periodically checked the results with a correct, hand-computed table.
- 8. working software in production testing code reviews version control pair programming high-availability architecture
- 9. Motivators Update application without breaking things! Validate functionality of updates Be able to trust deployment checks (in CI/CD workflow) Confirm that refactoring didn’t break existing functionality
- 10. Why do you skip tests? 45% 15% 5% 35% Too slow to run suite 35% Annoying extra step 15% Don’t see the point 5% Slows down deployment 45% 10
- 11. Frustrators It takes me an hour to write a single test My new tests just duplicate existing coverages so there’s no point (integration overlapping with unit) My suite fails all the time for no apparent reason…? It takes my test suite over 20 minutes to run, so I don’t run it locally Testing distracts me from my normal development workflow Setting up a testing environment is a huge pain It takes too long to deploy when I have a huge test suite
- 12. Frustrators It takes me an hour to write a single test My new tests just duplicate existing coverages so there’s no point (integration overlapping with unit) My suite fails all the time for no apparent reason…? It takes my test suite over 20 minutes to run, so I don’t run it locally Testing distracts me from my normal development workflow Setting up a testing environment is a huge pain It takes too long to deploy when I have a huge test suite
- 13. Using Docker can alleviate some frustrations associated with testing.
- 14. Testing with Docker Compose It’s easy, I promise
- 15. Docker and testing are a great pair. ❌ ✔
- 16. With Docker Compose, it is incredibly easy to create consistent, reproducible environments. ❌ ✔
- 17. Many of us already use Docker Compose to set up dev environments.
- 18. …But we stop there.
- 19. Use your Docker Compose environment for testing as well.
- 20. app: build: . command: rails server -p 3000 -b '0.0.0.0' volumes: - .:/app ports: - '3000:3000' links: - postgres postgres: image: postgres:9.4 A simple Rails app
- 21. ?! git clone && docker-compose up hackity hack How do I make tests happen? Development workflow
- 22. app: build: . command: rails server -p 3000 -b '0.0.0.0' volumes: - .:/app ports: - '3000:3000' links: - postgres postgres: image: postgres:9.4 A simple Rails app
- 23. app: build: . command: rspec spec volumes: - .:/app ports: - '3000:3000' links: - postgres postgres: image: postgres:9.4 A simple Rails app
- 25. In most cases, we need to do a bit of setup before running tests.
- 26. You might even need a different Dockerfile.
- 27. Docker Compose makes this easy app: build: . dockerfile: Dockerfile.test command: rake test volumes: - .:/app
- 28. 🚨 A word of warning! 🚨
- 29. 🚨 Race conditions! 🚨
- 30. You can also run one-off commands against a service with Docker Compose.
- 31. docker-compose run -e "RAILS_ENV=test" app rake db:setup docker-compose run -e "RAILS_ENV=test" app test-command path/to/spec.rb docker-compose up #-d if you wish Usual Docker Compose development environment Run rake task to set up db Then run tests against Docker services
- 32. Additional Docker Compose Testing Config Options environment: RACK_ENV: test
- 33. Additional Docker Compose Testing Config Options $ docker-compose up -d $ ./run_tests $ docker-compose stop $ docker-compose rm –f
- 34. Docker delivers a predictable, reproducible testing environment. Period.
- 35. Continuous Integration, Testing, and Docker Fail fast and not in production!
- 36. Continuous integration and testing go hand in hand. 👯
- 39. Relying on CI/CD without adequate test coverage is not a great idea.
- 40. Would you rather… ✔ 💩 Find out your code is broken by seeing a failed run of your CI/CD system? Find out your code is broken by seeing 500s on 500s on 500s in production?
- 41. What about running tests like this… …inside a container?
- 43. We run our unit tests in a conatiner during development, so we should do that during deployment too, right?
- 44. And if we’re running our services in containers during development, they should be running in containers in production, right?
- 45. 🚨 A word of warning! 🚨
- 46. —JérômePetazzoni “Docker-in-Docker is not 100% made of sparkles, ponies, and unicorns. 46
- 47. Docker in Docker
- 48. CAUTION! YMMV See https://jpetazzo.github.io - Mixing file systems == bad time - Shared build cache == bad time - Lots of other stuff == bad time
- 49. Shared daemon – what we really want
- 50. We get this by binding the Docker socket.
- 51. Parallel Testing with Docker Break it up.
- 52. Why do you skip tests? 45% 15% 5% 35% Too slow to run suite 35% Annoying extra step 15% Don’t see the point 5% Slows down deployment 45% 52
- 53. When developing, it’s easy to think of a container as a small VM that runs a specific workload.
- 54. ✔
- 55. But if we change our thinking to treat containers as just processes, then we can do some pretty cool stuff.
- 56. ✔
- 57. A syntax similar to Docker Compose for service definition… 57 web: build: image: my_app dockerfile_path: Dockerfile links: - redis - postgres redis: image: redis postgres: image: postgres
- 58. And use it to also define testing steps… 58 - type: parallel steps: - service: demo command: ruby check.rb - service: demo command: rake teaspoon suite=jasmine - service: demo command: rake test
- 59. - type: parallel steps: - service: demo command: some-test-command - service: demo command: another-test-command - service: demo command: yet-another-test-command Each step is run independently in a container 59
- 60. - service: demo command: some-test-command - service: demo command: another-test-command - service: demo command: yet-another-test-command And each container may be located in a range of availability zones 60
- 61. Test compose context Test runner jet test-1 test-0 test-3
- 62. Docker makes this possible by providing the means to create a predictable, reproducible testing environment.
- 63. Super Cool Tip™ Because quality is everyone’s problem.
- 64. Add an additional pipeline to fail builds if quality decreases.
- 65. Two good examples are code coverate and linting errors.
- 66. #!/bin/bash set –e ALLOWED_WARNINGS=100 #some arbitrary threshold warnings=`grep "offenses detected" rubocop.txt | cut -d " " –f4` if [ $warnings -gt $ALLOWED_WARNINGS ] then echo -e "033[31mallowed warnings $ALLOWED_WARNINGS033[0m" echo -e "033[31mactual warnings $warnings033[0m" echo -e "033[31mToo many rubocop warnings033[0m" echo -e "033[31mTry running 'bin/check_rubocop_against_master’033[0m" exit 1 else echo $warnings/$ALLOWED_WARNINGS is close enough ಠ_ಠ exit 0 fi
- 67. ✔ ✔ ❌ ❌
- 68. —Solomon(moreorless) “Improving quality is a lot of unglamourous work that really adds up.” 68
- 70. Highly recommended talks about development, testing, and lots of interesting stuff: https://speakerdeck.com/searls Ruby gem for parallel tests: grosser/parallel_tests Parallel Docker testing: Jet (from Codeship) CI/CD with Docker: http://pages.codeship.com/docker Running commands with Docker Compose: http://docs.docker.com/compose The perils of Docker-In-Docker: https://jpetazzo.github.io This talk: slideshare.net/rheinwein
- 71. —EdsgerDijkstra “Testing can be a very effective way to show the presence of bugs, but is hopelessly inadequate for showing their absence.” 71
- 72. Testing does not guarantee that our software works.
- 73. We test to know when our software is definitely broken.
- 74. Work harder to know when you’re wrong.