This snippet comes from Jamie Cansdale at TestDriven.net (http://weblogs.asp.net/nunitaddin/archive/2006/06/07/ClassLibrary-Projects-and-App.config.aspx)

In Visual Studio .NET 2003 if you want you unit tests to use an app config file you need to ensure a config file exists with the same path as your test assembly but ending with '.config'. Life has improved a bit with Visual Studio 2005 as it will automatically copy any 'App.config' file to the correct place even for ClassLibrary projects. You can achieve the same affect in VS2003 by using the following post-build event:

copy "$(ProjectDir)App.config" "$(TargetPath).config"

From http://blog.bleything.net/articles/2006/06/27/dry-out-your-database-yml:

login: &login
  adapter: mysql
  username: username
  password: password
  host: mysql.example.com

development:
  <<: *login
  database: app_dev

test:
  <<: *login
  database: app_test

production:
  <<: *login
  database: app_prod