Rspec，shoulda，validate_uniqueness_of，带有范围和错误的错误消息

I have following Rspec test:

我有以下Rspec测试：

describe Productlimit do

  before(:each) do 
    @productlimit = Factory.create(:productlimit, :user => Factory.create(:user))
  end

  subject { @productlimit }

  ...

  it { should validate_uniqueness_of(:price_cents).scoped_to(:direction_down, :currency, :market_id, :user_id) }
  ...
end
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