General information on how the migration works and testing specific portions.
The migration framework we are using.
To test a specific migration script, for example: 20131218142013_add_display_aspect_ratio_to_master_file.rb, you can run:
rake db:migrate:up VERSION=20131218142013
or if the version number is behind the current version number and you need to rerun if it if you later discover it didn't run properly the first time, run:
rake db:migrate:redo VERSION=20131218142013