Add more general feature test to guard against warning regressions

Author: PragTob

features/warnings.feature

@@ -0,0 +1,18 @@
+@rspec
+Feature:
+
+  Running SimpleCov with verbosity enabled does not yield warnings.
+
+  Background:
+    Given I'm working on the project "faked_project"
+
+  Scenario:
+    Given SimpleCov for RSpec is configured with:
+      """
+      require 'simplecov'
+      SimpleCov.start
+      """
+
+    When I successfully run `bundle exec rspec --warnings spec`
+    Then a coverage report should have been generated
+    And the output should not contain "warning"