phpunit/phpunit

.env.test

# define your env variables for the test env here
KERNEL_CLASS='App\Kernel'
APP_SECRET='$ecretf0rt3st'
SYMFONY_DEPRECATIONS_HELPER=999999
PANTHER_APP_ENV=panther
PANTHER_ERROR_SCREENSHOT_DIR=./var/error-screenshots

phpunit.xml.dist

<?xml version="1.0" encoding="UTF-8"?>

<!-- https://phpunit.readthedocs.io/en/latest/configuration.html -->
<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
         backupGlobals="false"
         colors="true"
         bootstrap="tests/bootstrap.php"
         convertDeprecationsToExceptions="false"
>
    <php>
        <ini name="display_errors" value="1" />
        <ini name="error_reporting" value="-1" />
        <server name="APP_ENV" value="test" force="true" />
        <server name="SHELL_VERBOSITY" value="-1" />
        <server name="SYMFONY_PHPUNIT_REMOVE" value="" />
        <server name="SYMFONY_PHPUNIT_VERSION" value="9.5" />
    </php>

    <testsuites>
        <testsuite name="Project Test Suite">
            <directory>tests</directory>
        </testsuite>
    </testsuites>

    <coverage processUncoveredFiles="true">
        <include>
            <directory suffix=".php">src</directory>
        </include>
    </coverage>

    <listeners>
        <listener class="Symfony\Bridge\PhpUnit\SymfonyTestsListener" />
    </listeners>

    <!-- Run `composer require symfony/panther` before enabling this extension -->
    <!--
    <extensions>
        <extension class="Symfony\Component\Panther\ServerExtension" />
    </extensions>
    -->
</phpunit>

tests/bootstrap.php

<?php

use Symfony\Component\Dotenv\Dotenv;

require dirname(__DIR__).'/vendor/autoload.php';

if (file_exists(dirname(__DIR__).'/config/bootstrap.php')) {
    require dirname(__DIR__).'/config/bootstrap.php';
} elseif (method_exists(Dotenv::class, 'bootEnv')) {
    (new Dotenv())->bootEnv(dirname(__DIR__).'/.env');
}