logging - RSpec:如何测试 Rails 记录器消息期望？

Question

我正在尝试测试 Rails 记录器是否接收我的某些规范中的消息。我正在使用Logging gem .

假设我有一个这样的类(class):

class BaseWorker

  def execute
    logger.info 'Starting the worker...'
  end

end

规范如下:

describe BaseWorker do

  it 'should log an info message' do
    base_worker = BaseWorker.new
    logger_mock = double('Logging::Rails').as_null_object
    Logging::Rails.stub_chain(:logger, :info).and_return(logger_mock)

    logger_mock.should_receive(:info).with('Starting the worker...')
    base_worker.execute
    Logging::Rails.unstub(:logger)
  end

end

我收到以下失败消息:

 Failure/Error: logger_mock.should_receive(:info).with('Starting worker...')
   (Double "Logging::Rails").info("Starting worker...")
       expected: 1 time
       received: 0 times

我尝试了几种不同的方法来让规范通过。例如，这有效:

class BaseWorker

  attr_accessor :log

  def initialize
    @log = logger
  end

  def execute
    @log.info 'Starting the worker...'
  end

end

describe BaseWorker do
  it 'should log an info message' do
    base_worker = BaseWorker.new
    logger_mock = double('logger')
    base_worker.log = logger_mock

    logger_mock.should_receive(:info).with('Starting the worker...')
    base_worker.execute
  end
end

但是必须像这样设置一个可访问的实例变量，这似乎是尾部在摇狗。 (实际上，我什至不确定为什么将记录器复制到 @log 会让它通过。)

测试日志记录的好解决方案是什么？

Answer 1

虽然我同意您通常不想测试记录器，但有时它可能很有用。

我在 Rails.logger 上取得了预期的成功。

使用 RSpec 已弃用的 should 语法:

Rails.logger.should_receive(:info).with("some message")

使用 RSpec 较新的 expect 语法:

expect(Rails.logger).to receive(:info).with("some message")

注意:在 Controller 和模型规范中，您必须将此行放在记录消息之前。如果你把它放在后面，你会收到如下错误消息:

Failure/Error: expect(Rails.logger).to receive(:info).with("some message")
       (#<ActiveSupport::Logger:0x007f27f72136c8>).info("some message")
           expected: 1 time with arguments: ("some message")
           received: 0 times