Add comments and appease RuboCop

Author: pirj

spec/spec_helper.rb

@@ -52,9 +52,15 @@ def self.run_all(reporter = nil)
   config.warnings = true
   config.raise_on_warning = true
 
+  # Execute a provided block with RSpec global objects (configuration,
+  # world, current example) reset. This is used to test specs with RSpec.
   config.around(:example) do |example|
-    RSpec::Core::Sandbox.sandboxed do |config|
-      RSpec::Rails.initialize_configuration(config)
+    # If there is an example-within-an-example, we want to make sure the inner
+    # example does not get a reference to the outer example (the real spec) if
+    # it calls something like `pending`.
+    RSpec::Core::Sandbox.sandboxed do |sandbox_config|
+      sandbox_config.before(:context) { RSpec.current_example = nil }
+      RSpec::Rails.initialize_configuration(sandbox_config)
       example.run
     end
   end