If you are planning on load testing your CD environment, you will need to copy not only the Azure Web Apps but also the databases and supporting services as well. In a scaled environment this means many databases and depending on your setup 3 or more web apps, plus potentially Solr servers too.
If you did not use ARM Templates or Terraform to setup your environment in the first place, there is no "quick" way to do this, you're going to have to identify the necessary pieces and copy them one at a time.
Start with the databases. Create a new SQL Server elastic pool and simply "restore" your Azure SQL DBs into this pool. You may need to restore the DB first then add it to the pool. You can rename the DBs after restoring from SQL Management Studio.
Copy Solr Services. If you are using a service like SearchStax you might be able to raise a ticket and ask them to clone your existing server. If you are operating Linux VMs in Azure you can snapshot the disk and clone the snapshot into a new VM.
Create a new Azure App Host. DO NOT USE THE EXISTING PROD HOST FOR LOAD TESTING. The purpose of a load test is to find the exhaustion point of a configuration. You WILL (SHOULD) denial-of-service your own website during the test, so you probably don't want to do that to your Production site.
Azure Web Apps can be "cloned" into a new host. This is the easiest way, otherwise you need to:
- create new web apps
- use the Kudu console or FTP to download all the files from the PROD sites to the new sites (Kudu can be used to upload the files too)
- copy the App Settings and Connection Strings from the prod sites' Web App Config to the new sites
- Update connection strings to ensure your apps are connected to the Databases you created earlier and the Solr you cloned
If you know exactly what to do, and your databases aren't too big (i.e. under 10GB) you can pull this off in about a day by hand. Properly scripted in about 30 minutes.