GitLab CI for Erlang Projects

GitLab CI is GitLab’s continuous integration software. It integrates with GitLab and runs your tests every time a commit is pushed to the remote repository. Getting it to run tests for projects written in Erlang can be a bit of hassle, so in this post I will share and explain my setup.

This post assumes that the gitlab_ci_runner user is already able to switch between Erlang versions using kerl. The kerl README has some simple usage instructions.

The CI runner (v5.0.0) is installed on an Ubuntu 14.04 machine and it talks to GitLab CI 5.2.1.

The build script that is used to run Erlang tests looks like this:

# Setup
source "$HOME/.kerl/installs/17.3/activate"
gitlabdir=$(basename "$(pwd)")
appdir=$(cat src/*.app.src | tr ',' '\n' | sed '2q;d' | tr -d ' ' | tr -d '\n')

# Rename directory
cd ..
rm -rf "$appdir"
mv "$gitlabdir" "$appdir"
cd "$appdir"

# Run tests
make dialyze
make tests

# Coverage
ls -rt $(find ./logs -name "cover.html") | tail -n 1 | xargs cat | grep -F 'Total' | awk '{gsub("<[^>]*>", "")}1'

# Cleanup
cd ..
mv "$appdir" "$gitlabdir"
cd "$gitlabdir"

Setup

This section activates an Erlang version and initializes two variables that hold directory names. gitlabdir is the name of current directory (e.g. project-1) and appdir is set to the name of the Erlang application that’s being tested. If the application name “detection” does not work for you, you can just hard code it.

Rename directory

Since GitLab CI names directories in a way that does not work with many Erlang tools, we have to manually move the project directory. This is because the directory in which an Erlang application resides has to be named like the application itself.

The rm is there to clean up any directories that might exist because of failed test runs.

Run tests

My projects use erlang.mk, which is why this part in the script might not work for your projects. You can easily fix this by replacing the two calls to make with whatever you use to run your tests.

Coverage

The test coverage is extracted from the latest cover.html file. It will be printed to stdout like this:

Total97 %742

Since we’re only interest in the 97, we can set the “Test coverage parsing” option to this regular expression: Total(\d+)\s\%.

Cleanup

In the end, all we have to do is to undo our changes to the directory structure that GitLab CI expects.

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