dummy.rb

# The contents of this block would be arbitrary, it's _not_ tied into any ORM/database/etc.
define_dummy(:stubbed_user) do |attrs|
  user = User.new(attrs)

  user.stub(:something).and_return('foo')

  user
end

describe User do
  describe '#something' do
    it 'returns something' do
      user = dummy(:stubbed_user, :name => 'Alice')

      # ...
    end
  end
end