The XML config that migrate-configuration rewrote

A configuration file dating from 2014 with attributes that had been deprecated for years and elements that had moved.

$ vendor/bin/phpunit --migrate-configuration
Created backup:         phpunit.xml.bak
Migrated configuration: phpunit.xml

# what it changed, in ours:
#   verbose="true"            → removed (now a CLI flag)
#   <filter><whitelist>       → <source><include>
#   convertDeprecations...    → <source> attributes
#   printerClass              → removed entirely

The tool does the right thing and the diff is worth reading rather than committing — ours removed a printerClass pointing at a custom output formatter that had been maintained since 2016, which was information rather than a problem. The backup file is what makes this safe to try, and deleting it afterwards is the step people forget.