Running a test restore will not actually save data to the endpoint you are restoring to. It loads the data into temporary files on the endpoint which are then deleted. 

Navigate to your backup portal and Click "Accounts" and then click "Users"

Click on the user account you would like to perform a test restore on

Click "Online" next to the device you would like to restore data to. This does not need to be the device that the backup job was attached to. 

Choose the vault you would like to run the restore from and click Next.

Click the drop-down arrow next to the device and the protected item you would like to restore the data from. 

Click the drop-down arrow next to the device you would like to restore data from. 

Click the arrow next to the protected item you would like to restore data from.

The restore prompt will only show you the most recent data. However, you can click the refresh button to load more snapshots.

Select the snapshot that you would like to restore from and click "Next"

Select the snapshot that you would like to restore.

You can choose to restore all items in the snapshot or select specific items.

If choosing specific items, you can drill down to the specific file to test. Once you have selected what you would like, click on "Next". 

If choosing specific items, you can drill down to the specific file to test. Once you have selected what you would like, click on next. 

Click on the dropdown and select "Simulate Restore Only" then click Restore.

Files and Folders
Simulate restore only
Program Input
Compressed archive file (zip / tar)
Microsoft Office 365

From there, you have triggered the test restore. You can now click on "Actions" and "View Job History"

Click "Report" next to the running restore job.

Click "Auto refresh" or keep clicking the refresh button until it has finished. 

The restore times will vary depending on the amount of data being tested as well as a number of external factors such as network bandwidth and file compression.

Once finished it will say if the test restore was successful or if it had any errors.