Testing with DB is sometimes done on the main DB instead of the test DB

It sounds like your tests are not using the correct database configuration. Here are a few steps to troubleshoot and ensure that your tests are using the test database:

1. Check the .env.testing file: Ensure that you have a .env.testing file in your project root. This file should contain the database configuration for your test environment. For example:

   DB_CONNECTION=mysql
   DB_DATABASE=testing
   DB_USERNAME=root
   DB_PASSWORD=
   

2. Ensure the phpunit.xml file is correctly configured: Your phpunit.xml file seems to be mostly correct, but double-check that the DB_DATABASE environment variable is set to testing:

   <php>
       <env name="APP_ENV" value="testing"/>
       <env name="DB_CONNECTION" value="mysql"/>
       <env name="DB_DATABASE" value="testing"/>
       <env name="DB_USERNAME" value="root"/>
       <env name="DB_PASSWORD" value=""/>
       <!-- other environment variables -->
   </php>
   

3. Check the config/database.php file: Ensure that your config/database.php file is set up to use the correct database connection when the environment is testing. It should look something like this:

   'connections' => [
       'mysql' => [
           'driver' => 'mysql',
           'host' => env('DB_HOST', '127.0.0.1'),
           'port' => env('DB_PORT', '3306'),
           'database' => env('DB_DATABASE', 'forge'),
           'username' => env('DB_USERNAME', 'forge'),
           'password' => env('DB_PASSWORD', ''),
           'unix_socket' => env('DB_SOCKET', ''),
           'charset' => 'utf8mb4',
           'collation' => 'utf8mb4_unicode_ci',
           'prefix' => '',
           'strict' => true,
           'engine' => null,
       ],
   ],
   

4. Clear the configuration cache: Sometimes, Laravel caches the configuration, and changes might not take effect immediately. Run the following commands to clear the cache:

   sail artisan config:cache
   sail artisan config:clear
   

5. Verify the environment during tests: Add a simple test to verify that the environment is set to testing and the database is correct:

   public function testEnvironmentIsTesting()
   {
       $this->assertEquals('testing', app()->environment());
       $this->assertEquals('testing', env('DB_DATABASE'));
   }
   

6. Check for hardcoded database connections: Ensure that none of your tests or application code is hardcoding the database connection. All database connections should be retrieved from the environment configuration.

By following these steps, you should be able to ensure that your tests are using the correct test database. If the issue persists, double-check for any typos or misconfigurations in your environment files and configuration settings.