In my test code I have a lot of boilerplate expressions "Magic", "return_". I also have lengthy strings to identify the paths of the functions to mock. The strings are not automatically replaced during refactoring and I would prefer to directly use the imported functions.
Example code:
from mock import patch, MagicMock
from pytest import raises
@patch(
'foo.baa.qux.long_module_name.calculation.energy_intensity.intensity_table',
MagicMock(return_value='mocked_result_table'),
)
Instead I would prefer:
from better_test_module import patch, Mock, raises
from foo.baa.qux.long_module_name.calculation import energy_intensity
@patch(
energy_intensity.intensity_table,
Mock('mocked_result_table'),
)
or
@patch(
energy_intensity.intensity_table,
'mocked_result_table',
)
I post my corresponding custom implementation as an answer below.
If you have other suggestions, please let me know. I am wondering why the proposed solution is not the default. I do not want to reinvent the wheel. Therefore, if there is an already existing library I could use, please let me know.
Related:
Create a wrapper module allowing for shorter names and passing functions directly. (If something like this already exists as a pip package, please let me know; don't want to reinvent the wheel.)
Usage:
from my_test_utils.mock import patch, Mock, raises
from foo.baa.qux.long_module_name.calculation import energy_intensity
@patch(
energy_intensity.intensity_table,
Mock('mocked_result_table'),
)
First draft for my wrapping code in my_test_utils/mock.py:
from mock import MagicMock, DEFAULT
from mock import patch as original_patch
from pytest import raises as original_raises
class Mock(MagicMock):
# This class serves as a wrapper for MagicMock to allow for shorter syntax
def __new__(cls, *args, **kwargs):
if len(args) > 0:
first_argument = args[0]
mock = MagicMock(return_value=first_argument, *args[1:], **kwargs)
else:
mock = MagicMock(**kwargs)
return mock
def assert_called_once(self, *args, **kwargs): # pylint: disable = useless-parent-delegation
# pylint did not find this method without defining it as a proxy
super().assert_called_once(*args, **kwargs)
def assert_not_called(self, *args, **kwargs): # pylint: disable = useless-parent-delegation
# pylint did not find this method without defining it as a proxy
super().assert_not_called(*args, **kwargs)
def patch(item_to_patch, *args, **kwargs):
if isinstance(item_to_patch, str):
raise KeyError('Please import and use items directly instead of passing string paths!')
module_path = item_to_patch.__module__
if hasattr(item_to_patch, '__qualname__'):
item_path = module_path + '.' + item_to_patch.__qualname__
else:
name = _try_to_get_object_name(item_to_patch, module_path)
item_path = module_path + '.' + name
item_path = item_path.lstrip('_')
return original_patch(item_path, *args, **kwargs)
def _try_to_get_object_name(object_to_patch, module_path):
module = __import__(module_path)
name = None
for attribute_name in dir(module):
attribute = getattr(module, attribute_name)
if attribute == object_to_patch:
if name is None:
name = attribute_name
else:
# object is not unique within its parent but used twice
message = (
'Could not identify item to patch because object is not unique.'
+ ' Please use a unique string path.'
)
raise KeyError(message)
if name is None:
raise KeyError('Could not identify object to patch.')
return name
def raises(*args):
# This function serves as a wrapper for raises to be able to import it from the same module as the other functions
return original_raises(*args)