Gemfile in email_inquire-0.9.0 vs Gemfile in email_inquire-0.10.0

@@ -7,9 +7,12 @@
 
 group :local do
   # Guard
   gem "guard-rspec", require: false
   gem "terminal-notifier-guard", require: false # OS X
+
+  # Mutation testing
+  gem "mutant-rspec", require: false
 end
 
 # Code coverage
 gem "codecov", require: false
 gem "simplecov", require: false