How to check for a change from Nil in RSpec

How to check for a change from Nil in RSpec

References

Reference NO 1

http://stackoverflow.com/questions/13654614/how-to-check-for-a-change-from-nil-in-rspec

Reference NO 2

http://stackoverflow.com/questions/13239929/nil-is-not-a-symbol-for-model-count-in-rspec-matcher

Reference NO 3

http://rspec.rubyforge.org/rspec/1.1.11/classes/Spec/Matchers.html

Reference NO 4

https://www.relishapp.com/rspec/rspec-expectations/docs/built-in-matchers

Reference NO 5

http://rubydoc.info/github/rspec/rspec-expectations/master/RSpec/Matchers

Reference NO 6

https://gist.github.com/663876

Reference NO 7

http://net.tutsplus.com/tutorials/ruby/ruby-for-newbies-testing-with-rspec/

Reference NO 8

http://everydayrails.com/2012/04/07/testing-series-rspec-controllers.html