Use casecmp instead of downcase ==

lib/t/cli.rb

@@ -221,7 +221,7 @@ def does_contain(user_list, user = nil)
     desc 'does_follow USER [USER]', 'Find out whether one user follows another.'
     method_option 'id', aliases: '-i', type: :boolean, desc: 'Specify user via ID instead of screen name.'
     def does_follow(user1, user2 = nil)
-      abort 'No, you are not following yourself.' if user2.nil? && user1 == @rcfile.active_profile[0].downcase
+      abort 'No, you are not following yourself.' if user2.nil? && @rcfile.active_profile[0].casecmp(user1).zero?
       abort "No, @#{user1} is not following themself." if user1 == user2
       require 't/core_ext/string'
       thread1 = if options['id']

lib/t/delete.rb

@@ -104,7 +104,7 @@ def mute(user, *users)
     def account(account, key = nil)
       if key && @rcfile.profiles[account].keys.length == 1
         continue = ask 'There is only one API key associated with this account, removing it will disable all functionality, are you sure you want to delete it? [y/N]'
-        return if continue.downcase != 'y'
+        return unless continue.casecmp('y').zero?
       elsif key
         return @rcfile.delete_key(account, key)
       else

lib/t/rcfile.rb

@@ -25,11 +25,11 @@ def find(username)
     end
 
     def find_case_insensitive_match(username)
-      profiles.keys.detect { |u| username.downcase == u.downcase }
+      profiles.keys.detect { |u| username.casecmp(u).zero? }
     end
 
     def find_case_insensitive_possibilities(username)
-      profiles.keys.select { |u| username.downcase == u.downcase[0, username.length] }
+      profiles.keys.select { |u| username.casecmp(u[0, username.length]).zero? }
     end
 
     def []=(username, profile)