ruby - 您如何测试是否会调用 Ruby 析构函数？

Question

我创建了一个类，我想将其卡在文件描述符上并在实例被 GC 处理时将其关闭。

我创建了一个看起来像这样的类:

class DataWriter
  def initialize(file)
    # open file
    @file = File.open(file, 'wb')
    # create destructor
    ObjectSpace.define_finalizer(self, self.class.finalize(@file))
  end

  # write
  def write(line)
    @file.puts(line)
    @file.flush
  end

  # close file descriptor, note, important that it is a class method
  def self.finalize(file)
    proc { file.close; p "file closed"; p file.inspect}
  end
end

然后我尝试像这样测试析构函数方法:

RSpec.describe DataWriter do
  context 'it should call its destructor' do
    it 'calls the destructor' do
      data_writer = DataWriter.new('/tmp/example.txt')
      expect(DataWriter).to receive(:finalize)
      data_writer = nil
      GC.start
    end
  end
end

运行此测试时，即使“file closed”与 file.inspect 一起打印，测试也会失败并输出以下内容:

1) DataWriter it should call its destructor calls the destructor
     Failure/Error: expect(DataWriter).to receive(:finalize)

       (DataWriter (class)).finalize(*(any args))
           expected: 1 time with any arguments
           received: 0 times with any arguments
     # ./spec/utils/data_writer_spec.rb:23:in `block (3 levels) in <top (required)>'

Answer 1

finalize 在 initialize 中被调用，返回 proc，并且再也不会被调用，所以你不能期望它在 finalization 时被调用。它是在实例完成时调用的 proc。要检查这一点，让 proc 调用一个方法而不是自己完成工作。这通过了:

class DataWriter
  # initialize and write same as above

  def self.finalize(file)
    proc { actually_finalize file }
  end

  def self.actually_finalize(file)
    file.close
  end

end

RSpec.describe DataWriter do
  context 'it should call its destructor' do
    it 'calls the destructor' do
      data_writer = DataWriter.new('/tmp/example.txt')
      expect(DataWriter).to receive(:actually_finalize)
      data_writer = nil
      GC.start
    end
  end
end