+1 to this

👍

I'm not super comfortable with adding a new method to the main object.

Shouldn't the following work already?

Motion::Project::App.setup do |app|
  if app.spec_mode
    Bundler.require :spec
  end
end

Any alternative way to require test-only gems? I'm doing this hacky thing:

if ARGV.join(' ') =~ /spec/
  Bundler.require :default, :spec
else
  Bundler.require
end

The app.spec_mode code works, my only qualm is that it doesn't feel like the right place to put Bundle.require; I would expect to see/put the require code at the top of the Rakefile.

I'm using app.spec_mode for config stuff like adding some fixtures to resources_dirs only when running tests:

  if app.spec_mode
    app.resources_dirs += ['spec/fixtures']
  end

But I'm not sure how some gems that tinker with the RM toolchain would behave if require is called within the config block :/