Asserting execution order in python unittest

Question

I have a function that creates a temporary directory, switches to that temporary directory, performs some work, and then switches back to the original directory. I am trying to write a unit test that tests this. I don't have a problem verifying that the current directory was changed to the temp dir and changed back again, but I'm having a problem verifying that the important stuff took place in between those calls.

My original idea was to abstract the function into three sub functions so that I could test the call order. I can replace each of the three sub functions with mocks to verify that they are called -- however, I am still presented with the issue of verifying the order. On a mock I can use assert_has_calls, but upon what object do I call that function?

Here is the class I'm trying to test:

import shutil
import os
import subprocess
import tempfile
import pkg_resources


class Converter:
    def __init__(self, encoded_file_path):
        self.encoded_file_path = encoded_file_path
        self.unencoded_file_path = None
        self.original_path = None
        self.temp_dir = None

    def change_to_temp_dir(self):
        self.original_path = os.getcwd()
        self.temp_dir = tempfile.mkdtemp()
        os.chdir(self.temp_dir)

    def change_to_original_dir(self):
        os.chdir(self.original_path)
        shutil.rmtree(self.temp_dir)

    def do_stuff(self):
        pass

    def run(self):
        self.change_to_temp_dir()
        self.do_stuff()
        self.change_to_original_dir()

This is as far as I got writing the test case:

def test_converter(self, pkg_resources, tempfile, subprocess, os, shutil):
    encoded_file_path = Mock()

    converter = Converter(encoded_file_path)
    converter.change_to_temp_dir = Mock()
    converter.do_stuff= Mock()
    converter.change_to_original_dir = Mock()

    assert converter.encoded_file_path == encoded_file_path
    assert converter.unencoded_file_path is None

    converter.run()

Now that I have each function mocked, I can verify THAT they were called, but not in what ORDER. How do I go about doing this?

Answer 1

One workaround would to be to create a separate mock object, attach methods to it and use assert_has_calls() to check the call order:

converter = Converter(encoded_file_path)
converter.change_to_temp_dir = Mock()
converter.do_stuff = Mock()
converter.change_to_original_dir = Mock()

m = Mock()
m.configure_mock(first=converter.change_to_temp_dir,
                 second=converter.do_stuff,
                 third=converter.change_to_original_dir)

converter.run()
m.assert_has_calls([call.first(), call.second(), call.third()])