pytest-layer-decorators

Reusable pytest decorators that enforce architectural layer separation in test suites.

Installation

pip install pytest-layer-decorators

Quick Start

1. Configure your layer module patterns

In your pyproject.toml:

[tool.pytest_layer_decorators]
domain_modules = ["myapp.domain.*"]
application_modules = ["myapp.application.*"]
infrastructure_modules = ["myapp.infrastructure.*"]
presentation_modules = ["myapp.presentation.*"]

Alternatively, in pytest.ini:

[pytest]
layer_domain_modules = myapp.domain.*
layer_application_modules = myapp.application.*
layer_infrastructure_modules = myapp.infrastructure.*
layer_presentation_modules = myapp.presentation.*

2. Decorate your tests

Apply the decorator directly to a test function or to a test class (the marker propagates to every test method inside the class).

from pytest_layer_decorators import domain, application, infrastructure, presentation
# ── style A: decorate individual test functions ──────────────────────
@domain
def test_entity_validation():
 from myapp.domain.models import Entity
 assert Entity("foo").name == "foo"
@application
def test_create_user_usecase():
 from myapp.domain.models import User
 from myapp.application.usecases import CreateUserUseCase
 ...
# ── style B: decorate a test class ───────────────────────────────────
@infrastructure
class TestDatabaseAdapter:
 def test_save(self):
 from myapp.infrastructure.db import Database
 ...
 def test_query(self):
 from myapp.infrastructure.db import Database
 ...
@presentation
class TestAPIController:
 def test_index_route(self):
 from myapp.presentation.api import UserController
 ...

3. Run pytest

Violations are reported at test setup time with clear messages:

ERROR test_domain.py::test_bad - Failed: Layer violation in test_domain.py::test_bad:
 test is marked @domain but imports from a restricted layer:
 - 'myapp.infrastructure.db' (belongs to 'infrastructure' layer, not allowed from 'domain' layer)
 @domain may only import from: nothing outside its own layer

Layer Dependency Rules

These rules mirror Clean Architecture / Hexagonal Architecture dependency flow: dependencies point inward, from outer layers (presentation, infrastructure) toward inner layers (application, domain).

Graceful Degradation

If no layer patterns are configured, the decorators still apply pytest markers but enforcement is disabled — no tests will be blocked. This allows incremental adoption.

License

MIT