Codeception/Symfony4 Environment variable not found: "DATABASE_URL"

I have a project in Symfony4 with doctrine DB, everything flies.

I would like to add some functional and unit testing with Codeception. I followed the docs and added this to my functional.suite.yml:

actor: FunctionalTestermodules:    enabled:        - Symfony:            app_path: 'src'            environment: 'test'        - Doctrine2:            depends: Symfony#            cleanup: true        - \Helper\Functional#       - Db    step_decorators: ~        

However, when running vendor/bin/codecept run I get an ugly:

In EnvVarProcessor.php line 131:

Environment variable not found: "DATABASE_URL".

I can't see anything else related in the docs, so not sure what I'm missing.