added unit tests for short_hash
added unit tests for short_hash

fxn/rails-contributors,gitlabhq/gitlab-contributors,gitlabhq/gitlab-contributors,amitsuroliya/rails-contributors,maclover7/rails-contributors,maclover7/rails-contributors,gitlabhq/gitlab-contributors,fxn/rails-contributors,maclover7/rails-contributors,amitsuroliya/rails-contributors,amitsuroliya/rails-contributors,fxn/rails-contributors,maclover7/rails-contributors,gitlabhq/gitlab-contributors,fxn/rails-contributors,amitsuroliya/rails-contributors