The output from Test-SPContentDatabase is pretty much unreadable IMHO, so as a quick top just use Format-table to control the formatting of standard output to get something actually readable!
[code]
PS C:\Users\[Your User]> Test-SPContentDatabase -Name [Name] -WebApplication [URL] | ft
it comes out much nicer!
[/code]
We’ve created a tool (and published it on codeplex) which provides detailed information by parsing the Test-SPContentDatabase output.
With this tool you will exactly know where your custom web parts are located and even more.
http://dev4side.com/projects/sharepoint-2010-extended-migration-db-attach-report.aspx
It would be great if you can try it and report a feedback/bugs on the codeplex site: http://sp2010extmigrareport.codeplex.com/discussions