Adding test for formatter

I have added database cleaner as for formatter spec it was trying to
use inbuild transactional fixture flag, which was failing as it
couldn't find any transaction to rollback. Hence switched to using
database_cleaner gem for using truncation as strategy

Gemfile

@@ -22,4 +22,5 @@ end
 
 group :test do
   gem 'test-unit'
+  gem 'database_cleaner'
 end