Rakefile in how_is-18.0.3 vs Rakefile in how_is-18.0.4

@@ -1,18 +1,23 @@
+# frozen_string_literal: true
+
 require 'bundler/gem_tasks'
 require 'rspec/core/rake_task'
 require 'timecop'
-#require 'vcr'
 require './spec/vcr_helper.rb'
 require 'how_is'
 
-RSpec::Core::RakeTask.new(:spec)
+RSpec::Core::RakeTask.new(:spec) do |t|
+  # Warning.warn() was added in Ruby 2.4.0, so don't use -w on older versions.
+  t.ruby_opts = '-w -r./spec/capture_warnings.rb' if RUBY_VERSION >= '2.4.0'
+end
 
 task :default => :spec
 
+# Helper functions used later in the Rakefile.
 class HelperFunctions
-  def self.freeze_time(&block)
+  def self.freeze_time(&_block)
     date = DateTime.parse('2016-11-01').new_offset(0)
     Timecop.freeze(date) do
       yield
     end
   end
@@ -24,10 +29,10 @@
       options = {
         repository: repository,
         format: format,
       }
 
-      cassette = repository.gsub('/', '-')
+      cassette = repository.tr('/', '-')
       VCR.use_cassette(cassette) do
         report = HowIs.generate_report(**options)
       end
 
       filename = "#{cassette}-report.#{format}"