如果使用不同的属性多次调用方法，如何模拟方法？

Question

I am writing unit tests for my Python and Fabric based code. I have following method which in turn calls sudo method of Fabric API multiple times with different arguments. I would like to know how to call assert on mock sudo object.

**main_file.py**

from fabric.api import sudo

def do_something(path_to_file_to_be_copied, destination_path):
    # remove file if already exists
    sudo('rm ' + path_to_file_to_be_copied, warn_only=True)
    sudo('cp ' + path_to_file_to_be_copied + ' ' + destination_path)

I have written test file as below :

**test_main_file.py**

import main_file

class MainFileTest(unittest.TestCase):

    @mock.patch('main_file.sudo')
    def test_do_something(self, mock_sudo):
        file_path = '/dummy/file/path.txt'
        dest_dir = '/path/to/dest/dir'
        main_file.do_something(file_path, dest_dir)
        mock_sudo.assert_called_with('rm ' + file_path)

Above test fails because mocked object remembers only last call. that is, if I write mock_sudo.assert_called_with(cp + file_path + ' ' + dest_dir) then test fails.

How can I assert both the calls to sudo ?

Answer 1

Try assert_any_call which asserts whether there has been any call, not just the most recent one.

Or, you can use call_args_list to get the list of args the mock has been called with.

Answer 2

assert_has_calls will do the job for you.

assert_has_calls : assert the mock has been called with the specified calls. The mock_calls list is checked for the calls.
If any_order is true then the calls can be in any order, but they must all appear in mock_calls.

import main_file
class MainFileTest(unittest.TestCase):

    @mock.patch('main_file.sudo')
    def test_do_something(self, mock_sudo):
        file_path = '/dummy/file/path.txt'
        dest_dir = '/path/to/dest/dir'
        main_file.do_something(file_path, dest_dir)
        mock_sudo.assert_has_calls(['rm ' + file_path,
                                    'cp' + file_path + ' ' + dest_dir],
                                     any_order=True)

Answer 3

I wrote a helper library to automatically generate the asserts for me.

Add those lines to print the correct asserts for your case, right after main_file.do_something(file_path, dest_dir) :

import mock_autogen.generator
print(mock_autogen.generator.generate_asserts(mock_sudo))

You would get the following output:

from mock import call

assert 2 == mock_sudo.call_count
mock_sudo.assert_has_calls(
    calls=[call('rm /dummy/file/path.txt', warn_only=True),
           call('cp /dummy/file/path.txt /path/to/dest/dir'), ])

No need to guess anymore, use mock-generator :)