moqpy 0.0.2

Extending unittest-mock with moq-like validators

pymoq

from pymoq.all import *

Following the end-to-end tutorial for nbdev.

Project homepage: github

Full documentation: documentation

Install

pip install pymoq

Quickstart

Suppose we have the following setup in a python backend.

from typing import Protocol

class IWeb(Protocol):
    "Interface for accessing internet resources"
    
    def get(self, url:str, page:int, verbose:bool=False) -> str:
        "Fetches the ressource at `url` and returns it in string representation"

class RessourceFetcher:
    base_url: str = "https://some_base.com/"
    
    def __init__(self, web: IWeb):
        self._web = web
    
    def check_ressource(self, ressource_name: str, page:int, verbose:bool=False) -> bool:
        url = self.base_url + ressource_name
        ressource = self._web.get(url, page, verbose)
        
        return ressource is not None

We want to test the fetch_ressource method of RessourceFetcher. More specifically, we want to test that if the ressource is correctly returned from the source, this method should return True, otherwise False.

Setting up the mock

mock = Mock(IWeb)
mock.get\
    .setup('https://some_base.com/ressource', int, False)\
    .returns(True)

fetcher = RessourceFetcher(mock)

If the call matches the siganture defined in the setup method, the lambda in returns is called and its return value is returned:

assert fetcher.check_ressource('ressource', 1)

If any part of the signature does not match, None is returned:

assert not fetcher.check_ressource('other_ressource', 1) # wrong ressource name
assert not fetcher.check_ressource('ressource', "1") # wrong type of page argument
assert not fetcher.check_ressource('ressource', "1", verbose=True) # wrong value for verbose argument

Verification

One might want to check how often a function mock was invoked with a specific call signature. This can easily be done via the .verify method:

mock = Mock(IWeb)
fetcher = RessourceFetcher(mock)

# setup
mock.get.setup(str, int, bool).returns(True)

# act
fetcher.check_ressource('ressource', 1)
fetcher.check_ressource('ressource', 2)
fetcher.check_ressource('ressource', 1, verbose=True)

# assert
mock.get.verify(str, int, bool).times(3)
mock.get.verify(str, int, bool).more_than(1)
mock.get.verify(str, int, bool).more_than_or_equal_to(3)
mock.get.verify(str, int, bool).less_than(4)
mock.get.verify(str, int, bool).less_than_or_equal_to(3)
mock.get.verify(str, str).never()

mock.get.verify(str, AnyInt('page', 2).less_than(2), bool).times(2)

Setup sequences

mock = Mock(IWeb)
mock.get.setup('resource', int, bool).returns_sequence([1,2,3])

assert mock.get('resource', 1, True)==1
assert mock.get('resource', 2, False)==2
assert mock.get('resource', 3, True)==3

print(mock.get('ressource', 1, True))

None

Setup exceptions

class WebException(Exception):
    """Exception that describes web-access errors"""

mock = Mock(IWeb)
fetcher = RessourceFetcher(mock)

# setup failing web call
mock.get.setup('https://some_base.com/unavailable_ressource', int, bool).throws(WebException())

# act and assert exception
with pytest.raises(WebException):
    fetcher.check_ressource('unavailable_ressource', 1, True)
    
# does not raise exception if call signature does not match
fetcher.check_ressource('available_ressource', 1, True);

Deep Dive

Refer to General Structure for more detail.

Things to add

• publish on pypi, conda