Install Shopware in a sub directory. It use same code, but no the same database. So you can test plugins.
1.) Install subdir project
mkdir public/your_subdir
cd public/your_subdir
git clone https://github.com/hlohaus/shopware-subdir-project.git .
2.) Copy database
3.) Copy .env to private/
4.) Change database name in .env
5.) Link folders
ln -s ../bundles/ .
ln -s ../media/ .
ln -s ../theme/ .
ln -s ../thumbnail/ .
6.) Open storefront