I would like to install SQL Server 2019 Developer Edition for test process in factory before purchase it
SQL Server 2019 dev edition is free. Starting from SQL Server 2014 DEV edition is basically free. You just need to cerate account with VS professional which is very easy.
How long I can use SQL Server 2019 Developer Edition 30 Days or ?
As long as you like, there is NO end date. This is not a evaluation edition which you can only use for 180 days. Just make sure you use it in dev environment for testing purpose only.