Miscellaneous updates to appease Rubocop

spec/spec_helper.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file was generated by the `rails generate rspec:install` command. Conventionally, all
 # specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
 # The generated `.rspec` file contains `--require spec_helper` which will cause
@@ -70,7 +72,7 @@ RSpec.configure do |config|
     # Use the documentation formatter for detailed output,
     # unless a formatter has already been configured
     # (e.g. via a command-line flag).
-    config.default_formatter = "doc"
+    config.default_formatter = 'doc'
   end
 
   # Print the 10 slowest examples and example groups at the