Unit tests for docker

In

Setup

  • Install Container Structure Test
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    curl -LO https://storage.googleapis.com/container-structure-test/latest/container-structure-test-linux-amd64 && \
    chmod +x container-structure-test-linux-amd64 && \
    sudo mv container-structure-test-linux-amd64 /usr/local/bin/container-structure-test
  • Select test options:
    • Command Tests: execute a command in your image and check the output
    • File Existence Tests: check if a file is, or isn’t, present in the image
    • File Content Tests: check the content of a file
    • Metadata Test: check if a container metadata is correct

Write unit tests

Prerequisites

  • a Dockerfile
  • a .yaml or .json file that contains your test cases

Example

  • Pre-existing code
    • Dockerfile
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      FROM ubuntu:bionic

      RUN apt-get update \
        && apt-get install -y curl gnupg \
        && curl -fsSL https://bazel.build/bazel-release.pub.gpg | gpg --dearmor > bazel.gpg \
        && mv bazel.gpg /etc/apt/trusted.gpg.d/ \
        && echo "deb [arch=amd64] https://storage.googleapis.com/bazel-apt stable jdk1.8" > /etc/apt/sources.list.d/bazel.list \
        && apt-get update \
        && apt-get install -y bazel \
        && rm -rf /var/lib/apt/lists/*

      RUN groupadd -g 1000 user \
        && useradd -d /home/user -m -u 1000 -g 1000 user \
        && chown -R user:user /home/user \
        && mkdir -p /bazel/cache \
        && chown -R user:user /bazel

      RUN echo "build --repository_cache=/bazel/cache">/home/user/.bazelrc
    • Build dockerfile
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      docker build -t docker-unit-test .
  • Unit Test code
    • unit-test.yaml
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      schemaVersion: '2.0.0'
      fileExistenceTests:
        - name: 'Check bazel cache folder exists and is owned by the non-root user'
          path: '/bazel/cache'
          shouldExist: true
          uid: 1000
          gid: 1000
          isExecutableBy: 'group'
      fileContentTests:
        - name: 'Validate cache folder config'
          path: '/home/user/.bazelrc'
          expectedContents: ['.*build --repository_cache=/bazel/cache.*']
    • Run the tests
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      container-structure-test test --image docker-unit-test --config unit-test.yaml

Automate testing

  • Automation with Ansible
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    - name: unit test Docker Image
      shell: |
        container-structure-test test --image {{ docker_image }} --config {{ test_file }}
        if $?
        then
          echo "Test Failed"
          exit 1
        else
          echo "Test Succeeded"
          exit 0
        fi