Custom Generators ignored

I want to add a spec for _form template, and then created a generators
the
inherit from Rspec::Generators::ScaffoldGenerator. What I have:

lib/generators/rspec_modded/scaffold/scaffold_generator.rb

require ‘generators/rspec/scaffold/scaffold_generator.rb’
module RspecModded
module Generators
class ScaffoldGenerator < Rspec::Generators::ScaffoldGenerator
def generate_view_specs
super
copy_view :_form
end
end
end
end

config/application.rb

module TestApp
class Application < Rails::Application
# …
config.generators do |g|
g.stylesheets false
g.assets false
g.helper false
g.integration_tool false

  g.test_framework :rspec_modded, fixture: false, 

fixture_replacement:
nil
g.fallbacks[:rspec_modded] = :rspec
end
end
end

If I run rails g the generator is there and works as expected when
manually run rails g rspec_modded:scaffold. However, during scaffold
the
test_framework is set to test_unit and I can’t figure out why!
With g.test_framework :rspec #... it works. I’ve tried to add
lib/generators in the autoload, to delete the passed options… Nothing
seems to work.