Add MockOf typing helper

[epenet]

Proposed change

Add some typing helpers for Mock, when used in conjuction with a class constructor.

It is completely pointless from a type-checking perspective (ie. mypy/pylance), but I think it makes the code more readable:

from tests.typing import MockOf

@pytest.fixture
def mock_api_client() -> MockOf[ApiClient]:
    """Fixture for ApiClient."""
    return Mock(spec=ApiClient)

async def test_blah(
    hass: HomeAssistant, mock_api_client: MockOf[ApiClient]
) -> None:
    """Test blah."""
    # Use it as an ApiClient
    assert isinstance(mock_api_client, ApiClient) # returns True
    d = Device(client=mock_api_client)

    # Use it as a Mock
    assert isinstance(mock_api_client, Mock) # also returns True
    assert mock_govee_api.start.assert_awaited_once()

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• Dependency upgrade
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• Breaking change (fix/feature causing existing functionality to break)
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• This PR fixes or closes issue: fixes #
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[cdce8p]

I don't think we should add that. As you point out yourself

It is completely pointless from a type-checking perspective (ie. mypy/pylance)

That also means it isn't validated at any point. We'd have to know to update the type annotation if the patch location or the mock object changes.

Yes, better typing for mocks is a valid issue but that's probably better solved at the Python typing level instead. I'd encourage you to look for / create a new discussion about it over at https://discuss.python.org/c/typing/32

[home-assistant]

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[epenet]

Adding some context:

• https://discuss.python.org/t/proposal-add-a-true-union-merge-join-intersection-type-annotation/39386
• Introduce an Intersection python/typing#213
• https://github.com/CarliJoy/intersection_examples/
• https://github.com/CarliJoy/intersection_examples/blob/main/docs/specification.rst

[epenet]

Interestingly, mypy is quite happy with the composite type MockOfApiClient.
Pylance treats it as Mock, but mypy does recognise that get_devices returns a list of strings.
Now if we could get mypy and pylance to recognise the Generic version that would be great.

"""Test MockOf for mypy."""

from typing import Generic, TypeVar
from unittest.mock import Mock

_T = TypeVar("_T")


class MockOf(Mock, Generic[_T]):
    """Add ability to set underlying type for Mock."""


class ApiClient:
    def get_devices(self) -> list[str]:
        return []


class MockOfApiClient(Mock, ApiClient):
    """Mock of ApiClient."""


mock_client = Mock(spec=ApiClient)
reveal_type(mock_client)
# Revealed type is "unittest.mock.Mock"
reveal_type(mock_client.get_devices)
# Revealed type is "Any"

mock_typed_client: MockOfApiClient = mock_client
reveal_type(mock_typed_client)
# Revealed type is "test_mypy.MockOfApiClient"
reveal_type(mock_typed_client.get_devices)
# Revealed type is "def () -> builtins.list[builtins.str]"

mock_generic_typed_client: MockOf[ApiClient] = mock_client
reveal_type(mock_generic_typed_client)
# Revealed type is test_mypy.MockOf[test_mypy.ApiClient] "
reveal_type(mock_generic_typed_client.get_devices)
# Revealed type is "Any"

[github-actions]

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