Run
composer dump-autoload & composer cache clean
to see this error
***"Warning: This development build of composer is over 60 days old. It is recommended to update it by running "/usr/local/bin/composer self-update" to get the latest version. Generated autoload files containing 580 classes
In DefinitionErrorExceptionPass.php line 54:
Cannot autowire service "App\Fixtures\PostFixtures": argument "$factory" of method "__construct()" references interface "App\Entity\PostFactoryInterface" but no such service exists. Did you create a class that implements this
interface?"***