Python fastapi ddd testing skill

Skill iktakahiro/python-fastapi-ddd-skill/skills/python-fastapi-ddd-testing-skill

A practical template for Building AI Agent Skills with Python, FastAPI, and Domain-Driven Design (DDD).

Install

npx -y skills add iktakahiro/python-fastapi-ddd-skill --skill python-fastapi-ddd-testing-skill

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

2 things to look at

no licenseNo license file was found in the repository. Code published without one is not open source by default, so using it at work is a question for whoever answers licensing questions where you are.
3 stars3 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.

What its author says it does

Copied from the file, not written here

Guides unit testing for Python DDD + Onion Architecture apps (Domain Entities/Value Objects and UseCases) using pytest and repository mocks, based on the dddpy reference. Use when adding tests, choosing what to mock, or structuring test folders for a DDD FastAPI project.

The file declares its own license as Apache-2.0. That is the author’s claim about this one file, and it is not the same thing as the license GitHub reports for the repository, which is listed with the other numbers below.

SKILL.md

1.9 KB, as published. Nobody here has run it

Testing DDD Layers with pytest (Domain / UseCase)

This skill focuses on unit tests for the inner layers:

Domain: Value Objects + Entities (pure business rules)
UseCase: application workflows that orchestrate Domain + Repository interfaces

It intentionally avoids full HTTP/API tests unless explicitly requested.

Test strategy (recommended)

Domain tests: no mocks, assert invariants and state transitions.
UseCase tests: mock repository interfaces (Mock(spec=...)), assert:
- correct repository method calls
- correct domain exceptions raised
- correct entity state transitions
Infrastructure/Presentation: add integration tests separately (optional).

Folder structure

Mirror the Onion layers:

tests/
  domain/{aggregate}/...
  usecase/{aggregate}/...
  infrastructure/...   # optional integration tests
  presentation/...     # optional API tests

UseCase testing pattern (dddpy-based)

Use unittest.mock.Mock(spec=RepoInterface) so typos fail fast.

from unittest.mock import Mock
import pytest

@pytest.fixture
def todo_repository_mock():
    return Mock(spec=TodoRepository)

def test_create_todo_calls_save(todo_repository_mock):
    usecase = CreateTodoUseCaseImpl(todo_repository_mock)
    title = TodoTitle("Test")

    todo = usecase.execute(title=title)

    todo_repository_mock.save.assert_called_once_with(todo)

For more examples (Value Object validation, entity lifecycle tests, and exception cases), read references/TESTING.md.