Stub Clients- Stub Heksher clients for testing and mocking

In order to unit test code that relies on Heksher settings, we can use these helper stub clients to mock whatever setting configuration we desire.

Code we want to test

from heksher.settings import Setting

background_color = Setting('background_color', str, default_value='blue',
                            configurable_features=['theme'])

def foreground_color(theme: str):
    """
    Return a color that is inverse to the current background color
    """
    back_rgb = color_name_to_rgb(background_color.get(theme=theme))
    fore_rgb = (255 - back_rgb[0], 255 - back_rgb[1], 255 - back_rgb[2])
    return color_rgb_to_name(fore_rgb)

How to test the above code in pytest with a stub client in pytest

from pytest import fixture
from heksher.clients.stub import SyncStubClient, Rule
from my_module import background_color, foreground_color

@fixture
def stub_client():
    with SyncStubClient() as stub_client:
        yield stub_client

def test_foreground_color(stub_client, monkeypatch):
    # will ensure that background_color.get() will return 'red'
    monkeypatch.setattr(stub_client[background_color], 'rules', 'red')
    assert foreground_color("any_theme") == 'cyan'

def test_foreground_color_by_theme(stub_client, monkeypatch):
    monkeypatch.setattr(stub_client[background_color], 'rules', [
            Rule({'theme': 'dark'}, 'black'),
            Rule({'theme': 'light'}, 'white'),
    ])
    assert foreground_color("dark") == 'white'
    assert foreground_color("white") == 'black'
    assert foreground_color("dracula") == 'yellow'  # default is still blue

class clients.stub.SyncStubHeksherClient(*args, **kwargs)

A stub client that can be used to mock a synchronous Heksher client. All arguments are ignored.

This class can be used as a context manager. Entering and exiting it does nothing.

__getitem__(setting: Setting[T]) → SettingPatcher[T]

Get a SettingPatcher that can be used to patch the given setting.

patch(setting: Setting, value: T | Collection[Rule[T]])

Patch the given setting with the given value.

Note

Using the patcher method is preferred.

Parameters:

• setting – The setting to patch

• value – The value to patch it with, or a collection of rules to patch it with. If rules are given, they must all address exactly the same context features in exactly the same order.

Returns:

A context manager that will restore the setting to its original value when exiting

reload

A MagicMock object that mocks the reload() method.

close

A MagicMock object that mocks the close() method.

ping

A MagicMock object that mocks the ping() method.

class clients.stub.AsyncStubHeksherClient(*args, **kwargs)

An async stub client that can be used to mock an async Heksher client. All arguments are ignored.

This class can be used as an async context manager. Entering and exiting it does nothing.

__getitem__(setting: Setting[T]) → SettingPatcher[T]

Get a SettingPatcher that can be used to patch the given setting.

patch(setting: Setting, value: T | Collection[Rule[T]])

Patch the given setting with the given value.

Note

Using the patcher method is preferred.

Parameters:

• setting – The setting to patch

• value – The value to patch it with, or a collection of rules to patch it with.

Returns:

A context manager that will restore the setting to its original value when exiting

reload

A AsyncMock object that mocks the reload() method.

close

A AsyncMock object that mocks the close() method.

ping

A AsyncMock object that mocks the ping() method.

class clients.stub.Rule(match_conditions: Mapping[str, str], value: T)

A rule used to patch a setting’s value depending on context features.

This class is a dataclass.

Parameters:

• match_conditions – A mapping of context feature names to their exact-match conditions.

• value – The value to patch the setting with when the conditions are met.

class clients.stub.SettingPatcher(...)

An object that can be used to patch a setting.

property rules

Set to this property either a single value, or a collection of Rules.

This property can be used to temporarily patch the setting with patchers like unittest.mock.patch or pytest’s monkeypatch fixture.