Do you run "Test-SPContentDatabase" before migration?

It is strongly recommend to run a pre-migration check on the SharePoint content database before attaching it to trigger the migration process.

Assumptions:

• You have already installed the customized wsp package you know
• You have restored the content database to SQL server
• You haven't attach the content database yet

Steps:

1. Run SharePoint PowerShell Console as administrator
2. Run the command below

Test-SPContentDatabase - name WSS_Content_DB  - webapplication http://sitename

3. Check the output log, ensure there isn't any errors