Provide env flag to disable asset caching, for CSS testing

lib/sidekiq/web.rb

@@ -143,13 +143,14 @@ module Sidekiq
       klass = self.class
       m = middlewares
 
+      rules = []
+      rules = [[:all, {"Cache-Control" => "public, max-age=86400"}]] unless ENV['SIDEKIQ_WEB_TESTING']
+
       ::Rack::Builder.new do
         use Rack::Static, urls: ["/stylesheets", "/images", "/javascripts"],
                           root: ASSETS,
                           cascade: true,
-                          header_rules: [
-                            [:all, {"Cache-Control" => "public, max-age=86400"}]
-                          ]
+                          header_rules: rules
         m.each { |middleware, block| use(*middleware, &block) }
         use Sidekiq::Web::CsrfProtection unless $TESTING
         run WebApplication.new(klass)

myapp/config/routes.rb

@@ -1,3 +1,6 @@
+# turns off browser asset caching so we can test CSS changes quickly
+ENV['SIDEKIQ_WEB_TESTING'] = '1'
+
 require 'sidekiq/web'
 Sidekiq::Web.app_url = '/'