GitLab CI pipelines

You can start by having a quick overview of the official introduction to pipelines and jobs documentation.

We are going to see how to make a pipeline as follows :

graph LR;
  subgraph build
  B(Build);
  end
  subgraph test
  C(Unit tests);
  D(Warnings tests);
  end
  B-->C
  B-->D

Artifacts

In order to use compilation build results in another test target, build results have to be saved as an artifact.

Let's modify the .gitlab-ci.yml file as follows :

stages:
    - build
    - test

job_build:
  stage: build
  tags:
    - linux
  script:
    - cd cxx
    - rm -rf build
    - mkdir build
    - cd build
    - cmake -DCMAKE_BUILD_TYPE=Debug ..
    - make 2>&1 | tee build.log
  artifacts:
    expire_in: 2 hrs
    paths:
      - cxx/build/

1. the test stage is added
2. make command outputs in the standard output, but also in a build.log file
3. cxx/build folder is saved as an artifact
4. ctest --output-on-failure to launch the unitary tests has been removed (it will have to be done on the following exercise).

Beware: The artifacts require to be ignored by git for not to face conflicts between jobs. Check cxx/build/ folder is present in the .gitignore file.

Exercise

Add a job_unit_test as a test stage that runs the unitary tests of the project from the job_build artefact.

Note: Do not forget to add a dependency on job_build.

Commit and push the .gitlab-ci.yml file and check the job_unit_test fails. We will fix it later.

Tips and tricks

You can use GitLab CI linter to validate your .gitlab-ci.yml file before pushing it.

Allow failure

Some tests require to be passed (like unitary tests). We would like to have a state passed with warnings on some other tests. We are going to use allow_failure in order to reach this state for compilation warnings.

Exercise

The command grep "warning:" build.log returns 0 (SUCCESS) when a warning is found in build.log file and 1 (FAILURE) when none was found. This is the exact contrary of what we want to do with GitLab (simulate the -Werror mecanism of the compiler g++). This is why we are going to use the following script:

grep "warning:" build.log; if [ $? -eq 1 ]; then exit 0; else exit 1; fi

as a new test stage that will be called job_warnings_test in the .gitlab-ci.yml file.

Note: Do not forget to add a dependency on job_build.

Commit and push the .gitlab-ci.yml file and check the job_warnings_test fails, but is allowed to fail. This corresponds to the state passed with warnings We will fix it later.

Warnings and tests fix

googletest provides a macro for this:

EXPECT_NEAR(expected, actual, absolute_error)

Exercise

Fix the warning and the test failure in tests/TestSphere.cpp using this function. 1e-5 is a reasonable absolute error value.

Commit and push the tests/TestSphere.cpp file and check the compilation and tests are now passed with warnings (because a warning in bench.cpp is remaining).

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