symfony4: how do I configure dataFixture to write in test db - unit-testing

Question

I want to load the testdata for my unit tests into the test db via DataFixtures.
The documentation says, that if I set the environment variable the test db should be used:
$ php bin/console doctrine:fixtures:load --env=test
Careful, database will be purged. Do you want to continue y/N ?y
> purging database
> loading App\DataFixtures\PropertyFixtures
> loading App\DataFixtures\UserFixtures
> loading App\DataFixtures\UserPropertyFixtures
However if I check the data end up in my default database.
Where do I configure my test db with symfony 4?
And where do I configure it, so that DataFixtures knows where to write?
For my functional tests I configured the db setting in the phpunit.xml

Answer 1

What we did to solve it was the following. I don't know if that is a good way, so alternative solutions are still appreciated.
in ../config/packages there is the file doctrine.yaml
I copied the file in the folder ./config/packages/test and edited it in the following way:
parameters:
# Adds a fallback DATABASE_URL if the env var is not set.
# This allows you to run cache:warmup even if your
# environment variables are not available yet.
# You should not need to change this value.
env(DATABASE_URL): ''
doctrine:
dbal:
# configure these for your database server
driver: 'pdo_mysql'
server_version: '5.7'
charset: utf8
default_table_options:
charset: utf8
collate: utf8_unicode_ci
url: mysql://%db_user_test%:%db_password_test%#%db_host_test%:%db_port_test%/%db_name_test%
orm:
auto_generate_proxy_classes: '%kernel.debug%'
naming_strategy: doctrine.orm.naming_strategy.underscore
auto_mapping: true
mappings:
App:
is_bundle: false
type: annotation
dir: '%kernel.project_dir%/src/Entity'
prefix: 'App\Entity'
So what I changed was the like with the url: mysql....
In my parameters I had added the parameters db_user_test etc and used them to connect to the test db.
It works, but still I am not sure if this is how it should be done.