In Symfony you can define some configuration in the .env file. To be sure of the value the program actually receives at runtime, there is the following command
php bin/console debug:container --env-var=DATABASE_URL --env=test
With this command you can easily see the value Symfony uses
php bin/console debug:container --env-var=DATABASE_URL Symfony Container Environment Variables ======================================= // Displaying detailed environment variable usage matching DATABASE_URL %env(resolve:DATABASE_URL)% --------------------------- ----------------- ----------------------------------------------------------------- Default value n/a Real value "%env(resolve:DATABASE_URL_DOCKER)%" Processed value "mysql://root:rooot@db:3306/database" ----------------- ----------------------------------------------------------------- // Note real values might be different between web and CLI.