Missing required arguments: aws_access_key_id, aws_secret_access_key on rake test

I'm doing chapter 11 of hartle's tutorial. When I ran heroku run rake db:migrate I got this error:

Missing required arguments: aws_access_key_id, aws_secret_access_key

I solved it with the answer in enter link description here and migrate successfully.but now when I run

bundle exec rake test

It gives me:

rake aborted!
ArgumentError: Missing required arguments: aws_access_key_id, aws_secret_access_key

This is my carrierwave file:

CarrierWave.configure do |config|
  config.fog_credentials = {
    :provider               => 'AWS',
    :aws_access_key_id      => ENV['S3_KEY'],
    :aws_secret_access_key  => ENV['S3_SECRET'],
    :region                 => ENV['S3_REGION'],
    :endpoint               => ENV['S3_ENDPOINT']
  }

  if Rails.env.test? || Rails.env.development?
    config.storage = :file
    config.enable_processing = false
    config.root = "#{Rails.root}/tmp/uploads/#{DateTime.now.to_f}.#{rand(999)}.#{rand(999)}"
  else
    config.storage = :fog
  end

  config.cache_dir = "#{Rails.root}/tmp/uploads/#{DateTime.now.to_f}.#{rand(999)}.#{rand(999)}"
  config.fog_directory  = ENV['S3_BUCKET_NAME']
  config.fog_public     = false
  config.fog_attributes = {}
end

I tested the answer in enter link description here and it didn't work for me.