pytest-automock

Reason

• No generic automock solution

Features

• Pytest plugin
• Autogenerate/autouse mocks for functions and objects
• Sync and async support
• Locked mode to be sure mocked objects stay untouched
• Customizable serialization

Limitaions

• No support for dunder methods (can be partly solved in future)
• No support for sync/async generators/contexts
• Races will break tests, since order counts

License

pytest-automock is offered under MIT license.

Requirements

• python 3.6+

Usage

Lets say you have some module mymod.py:

import time

class Network:
    def get_data_from_network(self, x, y):
        time.sleep(1)
        return x + y

    def send_data_to_network(self, value):
        time.sleep(1)

def logic(x):
    n = Network()
    a, b = 0, 1
    while b < x:
        c = n.get_data_from_network(a, b)
        a, b = b, c
        n.send_data_to_network("ok")
    return b

And you want to create mocks for your Network class (since testing time and sane counts), but you are too lazy to write them... conftest.py:

import pytest
import mymod

@pytest.fixture(autouse=True)
def _mocks(automock):
    with automock((mymod, "Network")):
        yield

test_logic.py:

from mymod import logic

def test_logic():
    assert logic(7) == 8
    assert logic(10) == 13

If you run pytest on this setup, then you will see fail:

$ pytest -x
...
E           RuntimeError: Mock is locked, but '__init__' wanted

automock can work in two modes: locked and unlocked. Locked mode is default, real methods calls of mocked objects are not allowed in this mode. So, above error says that we can't call __init__ of our Network. In locked mode there is no mock-files update also.

To allow real calls and mocks generation automock provides extra cli argument to pytest: --automock-unlocked

$ pytest -x --automock-unlocked
...
test_logic.py .
...
1 passed in 22.09s

After that you can see that tests/mocks/test_logic/mymod/Network file was created. This is mock for your test sequence. Now you can rerun tests and see what happens (you can omit --automock-unlocked key for ensurance, that real object will not be touched (actually even created)).

$ pytest -x
...
test_logic.py .
...
1 passed in 0.04s

API

automock (fixture)

automock fixture is a context manager

def automock(*pairs,
             storage: Union[str, Path] = "tests/mocks",
             override_name: Optional[str] = None,
             unlocked: Optional[bool] = None,
             encode: Callable[[Any], bytes] = pickle.dumps,
             decode: Callable[[bytes], Any] = pickle.loads)

• *pairs: pair/tuple of object/module and attribute name (str)
• storage: root path for storing mocks
• override_name: forced mock-file name
• unlocked: mode selector (if omited, selected by --automock-unlocked)
• encode: encode routine
• decode: decode routine

automock_unlocked (fixture)

Fixture with default mode from cli parameter (bool).

automock (function)

automock function is not supposed to be used by anyone but automock fixture

def automock(factory: Callable, *,
             memory: Dict,
             locked: bool = True,
             encode: Callable[[Any], bytes] = pickle.dumps,
             decode: Callable[[bytes], Any] = pickle.loads):

• factory: object/function to wrap
• memory: dicrionary to get/put mocks
• locked: mode selector
• encode: encode routine
• decode: decode routine

Development

Run tests

Since coverage issue/feature, plugins coverage is broken by default. Workaround:

COV_CORE_SOURCE=pytest_automock COV_CORE_CONFIG=.coveragerc COV_CORE_DATAFILE=.coverage.eager pytest