gitlab-org--gitlab-foss/doc/ci/examples/test-phoenix-application.md

## Test a Phoenix application

This example demonstrates the integration of Gitlab CI with Phoenix, Elixir and
Postgres.

### Add `.gitlab-ci.yml` file to project

The following `.gitlab-ci.yml` should be added in the root of your
repository to trigger CI:

```yaml
image: elixir:1.3

services:
  - postgres:9.6

variables:
  MIX_ENV: "test"

before_script:
  # Setup phoenix dependencies
  - apt-get update
  - apt-get install -y postgresql-client
  - mix local.hex --force
  - mix deps.get --only test
  - mix ecto.reset

test:
  script:
    - mix test
```

The variables will set the Mix environment to "test". The
`before_script` will install `psql`, some Phoenix dependencies, and will also
run your migrations.

Finally, the test `script` will run your tests.

### Update the Config Settings

In `config/test.exs`, update the database hostname:

```elixir
config :my_app, MyApp.Repo,
  hostname: if(System.get_env("CI"), do: "postgres", else: "localhost"),
```

### Add the Migrations Folder

If you do not have any migrations yet, you will need to create an empty
`.gitkeep` file in `priv/repo/migrations`.

### Sources

- https://medium.com/@nahtnam/using-phoenix-on-gitlab-ci-5a51eec81142
- https://davejlong.com/ci-with-phoenix-and-gitlab/