fix clear path, fix env var

Author: rmosolgo

test/react/server_rendering/webpacker_manifest_container_test.rb

@@ -20,7 +20,7 @@ class WebpackerManifestContainerTest < ActiveSupport::TestCase
     def test_it_loads_from_webpack_dev_server
       webpack_dev_server = fork do
         Dir.chdir("test/dummy") do
-          exec "./bin/webpack-dev-server RAILS_ENV=development"
+          exec "RAILS_ENV=development ./bin/webpack-dev-server "
         end
       end
 

test/support/webpacker_helpers.rb

@@ -1,5 +1,5 @@
 module WebpackerHelpers
-  PACKS_DIRECTORY =  File.expand_path("../dummy/public/packs", __FILE__)
+  PACKS_DIRECTORY =  File.expand_path("../../dummy/public/packs", __FILE__)
 
   module_function
   def available?