Python 模拟映射\u异步函数参数生成PicklingError

试图围绕执行

map\u async（）

操作的函数编写一些单元测试。更具体地说，我想确认在其中一个进程中发生异常时，某些文件会被清除。下面提供了带有意图的示例伪代码

福比

def write_chunk(chunk):
    ... create file from chunk
    return created_filename

class Foo:
    def write_parallel(chunks):
        filenames = set()
        try:
            pool = Pool(processes=2)
            pool.map_async(write_chunk, chunks, callback=filenames.add)
        except Exception:
            //handle exception
        finally:
            cleanup_files(filenames)

def write_chunk(chunk):
    return write_chunk_wrapped(chunk)

def write_chunk_wrapped(chunk)
    ... create file from chunk
    return created_filename

class Foo:
    def write_parallel(chunks):
        filenames = set()
        try:
            pool = Pool(processes=2)
            pool.map_async(write_chunk, chunks, callback=filenames.add)
        except Exception:
            //handle exception
        finally:
            cleanup_files(filenames)

测试_foo.py

@patch("foo.write_chunk")
def test_write_parallel_exception_cleanup(self, mock_write_chunk):
    def mock_side_effect(chunk):
        if "chunk_1" == chunk:
            raise Exception
        else:
            return chunk
    mock_write_chunk.side_effect = mock_side_effect

    foo = Foo()
    foo.write_parallel({"chunk_1", "chunk_2"})
    //assert "chunk_2" cleaned up and exception is thrown.

@patch("foo.write_chunk_wrapped")
def test_write_parallel_exception_cleanup(self, mock_write_chunk_wrapped):
    def mock_side_effect(chunk):
        if "chunk_1" == chunk:
            raise Exception
        else:
            return chunk
    mock_write_chunk_wrapped.side_effect = mock_side_effect

    foo = Foo()
    foo.write_parallel({"chunk_1", "chunk_2"})
    //assert "chunk_2" cleaned up and exception is thrown.

但是，当我执行测试时，我得到以下PicklingError:

PicklingError:cannotpickle:它与mock.MagicMock

不是同一个对象

---

你知道如何用我自己的模拟函数替换映射函数的预期结果吗？

因此，由于问题源于试图模拟和Pickle函数，我决定将该函数拉到一个单独的函数，模拟该函数，同时允许对原始函数进行Pickle。见下文：

福比

def write_chunk(chunk):
    ... create file from chunk
    return created_filename

class Foo:
    def write_parallel(chunks):
        filenames = set()
        try:
            pool = Pool(processes=2)
            pool.map_async(write_chunk, chunks, callback=filenames.add)
        except Exception:
            //handle exception
        finally:
            cleanup_files(filenames)

def write_chunk(chunk):
    return write_chunk_wrapped(chunk)

def write_chunk_wrapped(chunk)
    ... create file from chunk
    return created_filename

class Foo:
    def write_parallel(chunks):
        filenames = set()
        try:
            pool = Pool(processes=2)
            pool.map_async(write_chunk, chunks, callback=filenames.add)
        except Exception:
            //handle exception
        finally:
            cleanup_files(filenames)

测试_foo.py

@patch("foo.write_chunk")
def test_write_parallel_exception_cleanup(self, mock_write_chunk):
    def mock_side_effect(chunk):
        if "chunk_1" == chunk:
            raise Exception
        else:
            return chunk
    mock_write_chunk.side_effect = mock_side_effect

    foo = Foo()
    foo.write_parallel({"chunk_1", "chunk_2"})
    //assert "chunk_2" cleaned up and exception is thrown.

@patch("foo.write_chunk_wrapped")
def test_write_parallel_exception_cleanup(self, mock_write_chunk_wrapped):
    def mock_side_effect(chunk):
        if "chunk_1" == chunk:
            raise Exception
        else:
            return chunk
    mock_write_chunk_wrapped.side_effect = mock_side_effect

    foo = Foo()
    foo.write_parallel({"chunk_1", "chunk_2"})
    //assert "chunk_2" cleaned up and exception is thrown.