我创建了一个我想挂在文件描述符上的类,并在实例经过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,即使将“ filecloses”和“ file.inspect”一起打印,测试也会失败,并显示以下输出:
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)>'
finalize
在中调用initialize
,返回proc,然后再也不会调用它,因此您不能期望在完成时调用它。实例完成后会调用此proc。要进行检查,请让proc调用方法而不是自己完成工作。通过:
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
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