URGENT! How do I solve the following error?

I am trying to run a test using rspec and I am getting the following error. Please help.

ReactOnRails: Set generated_assets_dir to default: public/webpack/development
rake aborted!
NameError: undefined local variable or method `webpack' for main:Object

There are some fixes for this issue here: https://github.com/shakacode/react_on_rails/issues/956

Are any of these helpful to you?