Testing Strategies for

Docker Containers

Alexei Ledenev @alexeiled

About me…•DT @HPE

•github.com/alexei-led/pumba

•#docker, #golang, #aws

•medium.com/@alexeiled

•@alexeiled

Why Docker• Portability

• Speed

• Configuration

• Docker Hub (“App Store”)

Docker Architecture

Demo App & Test• Demo App

• Rest API server

• #golang

• Test

• Newman

• Postman scenario file

• #nodejs

The “Naive” Approach

#builddemoapp$gobuild-o.dist/demo-v

#runappandtests$.dist/demo&>/dev/null&$newmanrun-etest/local.env.jsondemo-rest-api-tests.postman.json

#buildDockerdemoimage$dockerbuild-tdemo-fdocker/Dockerfile.dist.

https://asciinema.org/a/100204

Benefits and Drawbacks• Familiar CI flow

• Application portability

• Smaller Docker image

• Non portable DEV environment

• Non portable TEST environment

App & Test Container

#builddemoapp&testcontainer$dockerbuild-tdemo:apptest-fdocker/Dockerfile.build.apptest.

#runtests$dockerrun-it--rmdemo:apptestscript/test.sh

#runapp$dockerrun-d-p10000:10000demo:apptestdemo

https://asciinema.org/a/100216

Benefits and Drawbacks• Application portability

• Portable DEV environment

• Portable TEST environment

• Bigger Docker image size

• Need to rebuild the whole image on code or test change

• Polluted Docker image

• Need to manage test results

Test Aware Container

#buildtestawareDockerimage$dockerbuild-tdemo:testaware-fdocker/Dockerfile.build.testaware.

#runtests$dockerrun-it--rmdemo:testaware

#getapplayersfromimage$APP_LAYER=$(dockerhistorydemo:testaware|\grep-e“LABELSPLIT=T”|\awk‘{print$1}’)

#tagAPP_LAYERandpushit$dockertag$APP_LAYERdemo:app

#rundemoapp$dockerrun-it—rm-p10000:10000demo:app

https://asciinema.org/a/100260

Benefits and Drawbacks• Application portability

• Portable TEST and DEV environments

• 2 separate images

• One Dockerfile

• Need to rebuild the whole image on code or test change

• Need some shell “magic” to create a clean APP image (non-Docker way)

– Me :-)

“After trying multiple approaches, the following is the one that I can recommend.”

Docker Automation Flow• Docker automation CI/CD flow consists from multiple steps, like: build, scan, test,

run, deploy and others.

• Each step requires different tools, runtime, packages, data and configuration files

• Use dedicated Docker container for every step

• For example:

• Builder Container - use it to build your app. Docker container with compilers, linters, package managers and other dev tool.

• Test Container(s) - user it to test your app. Docker container with testing tools, test scripts, runtimes and helper files and required packages.

• App Container - the one you push/deploy. Docker container with application binary, runtime and required packages only.

#buildBuildContainerimage$dockerbuild-tdemo:builder-fdocker/Dockerfile.builder.

#useBuildercontainertobuildtheapp$dockerrun-it--rm\-v$(pwd)/.dist:/go/src/app/.dist\-eCGO_ENABLED=0demo/buildergobuild-v-o.dist/demo

#buildAppContainerimage$dockerbuild-tdemo:dist-fdocker/Dockerfile.dist.

#buildTestContainerimage$dockerbuild-tdemo:test-fdocker/Dockerfile.test.

#createcommonnetworkforappandtest$dockernetworkcreatemynet

#rundemoapp$dockerrun-d--namedemo--networkmynetdemo:dist

#runtests$dockerrun-d--nametests--networkmynetdemo:test\newmanrun-etest/demo.env.json\test/demo-rest-api-tests.postman.json

CI with Test Containers

Benefits and Drawbacks• Application portability • Portable DEV environment

• Build ANYWHERE • Portable TEST environment

• Test ANYWHERE • Small APP image • Fast builds

• Need an approach/tool to automate and orchestrate Docker build flow • Bash, Ansible, etc. • Docker CI/CD service, like

codefresh.io

Q&A

@alexeiled