当方法调用 .backtrace 时在 Rspec 中模拟错误消息

Question

我有一个记录错误的方法。它以错误消息作为参数，但现在它需要一个完整的错误并在其上调用 .backtrace。方法如下：

def log_error(error)
    puts error.backtrace
    puts "RECONCILE_TAX_RATES [#{Time.now}] ERROR [#{error.message}]"
  end

我正在尝试对其进行测试，但我无法弄清楚测试的语法。我之前有的是：

it 'logs errors' do
    time = "Tue, 16 Sep 2014 20:18:19 UTC +00:00"
    Timecop.freeze(time) do
      tax_reconciler = TaxReconciler.new
      error_message = "I'm sorry, Dave. I'm afraid I can't do that."
      expected = "RECONCILE_TAX_RATES [2014-09-16 20:18:19 UTC] ERROR [I'm sorry, Dave. I'm afraid I can't do that.]"

      STDOUT.should_receive(:puts).with(expected)
      tax_reconciler.log_error(error_message)
    end
  end

我尝试了 rSpec 文档中的各种组合，但我一直被 .backtrace 方法绊倒。如何模拟此错误消息以使 .backtrace 不会爆炸？提前感谢您的帮助，如果我需要提供更多信息，请告诉我。

编辑：对于任何有类似问题的人，我使用的解决方案是：

 it 'logs errors' do
    time = "Tue, 16 Sep 2014 20:18:19 UTC +00:00"
    Timecop.freeze(time) do
      expected = "RECONCILE_TAX_RATES [2014-09-16 20:18:19 UTC] ERROR [I'm sorry, Dave. I'm afraid I can't do that.]"
      tax_reconciler = TaxReconciler.new
      begin
        raise "I'm sorry, Dave. I'm afraid I can't do that."
      rescue => error_message
        STDOUT.should_receive(:puts).with(expected)
        STDOUT.should_receive(:puts).with(error_message.backtrace)
        tax_reconciler.log_error(error_message)
      end
    end
  end

Answer 1

我会这样做：

describe '#log_error' do
  let(:time)    { 'Tue, 16 Sep 2014 20:18:19 UTC +00:00' }
  let(:message) { 'The message' }
  let(:error)   { double(:message => message, :backtrace => []) }
  let(:line)    { 'RECONCILE_TAX_RATES [2014-09-16 20:18:19 UTC] ERROR [The message]' }

  subject(:tax_reconciler) { TaxReconciler.new }

  before { allow(STDOUT).to receive(:puts) }

  it 'logs errors' do
    Timecop.freeze(time) do
      tax_reconciler.log_error(error)
      expect(STDOUT).to have_receive(:puts).with(line)
    end
  end
end