fix usage of Sprockets::Manifest in test

Author: rmosolgo

test/react/server_rendering/manifest_container_test.rb

@@ -1,24 +1,28 @@
 require "test_helper"
 
-class ManifestContainerTest < ActiveSupport::TestCase
-  def setup
-    precompile_assets
+# Rails 3.x doesn't have `application.assets_manifest=`
+# I don't think we have to support Rails 3 + Sprockets 3 anyways!
+if Rails::VERSION::MAJOR > 3
+  class ManifestContainerTest < ActiveSupport::TestCase
+    def setup
+      precompile_assets
 
-    # Make a new manifest since assets weren't compiled before
-    config = Rails.application.config
-    path = File.join(config.paths['public'].first, config.assets.prefix)
-    new_manifest = Sprockets::Manifest.new(Rails.application.assets, path, config.assets.manifest)
-    Rails.application.assets_manifest = new_manifest
+      # Make a new manifest since assets weren't compiled before
+      config = Rails.application.config
+      path = File.join(config.paths['public'].first, config.assets.prefix)
+      new_manifest = Sprockets::Manifest.new(Rails.application.assets, path)
+      Rails.application.assets_manifest = new_manifest
 
-    @manifest_container = React::ServerRendering::ManifestContainer.new
-  end
+      @manifest_container = React::ServerRendering::ManifestContainer.new
+    end
 
-  def teardown
-    clear_precompiled_assets
-  end
+    def teardown
+      clear_precompiled_assets
+    end
 
-  def test_find_asset_gets_asset_contents
-    application_js_content = @manifest_container.find_asset("application.js")
-    assert(application_js_content.length > 50000, "It's the compiled file")
+    def test_find_asset_gets_asset_contents
+      application_js_content = @manifest_container.find_asset("application.js")
+      assert(application_js_content.length > 50000, "It's the compiled file")
+    end
   end
 end