testing.rst

Writing tests with blacksmith

In software development, the testability of the code is the key of software quality.

Using blacksmith, no mock are necessary to test the code. The correct way of testing call is to implement an AbstractTransport ( :class:`blacksmith.AsyncAbstractTransport` or :class:`blacksmith.SyncAbstractTransport`) with response the :class:`blacksmith.HTTPResponse`.

Implement a FakeTransport

The fake transport implementation has to be passed to the ClientFactory at the instantiation.

Using pytests the fake transport responses can be parametrized.

Example of fake transport:

.. literalinclude:: testing_01.py

Then, you need a dependency injection to properly initialize the client.

In the example below, we are injecting the transport in a FastAPI service.

.. literalinclude:: testing_02.py
   :emphasize-lines: 10

We can see that if a transport is passed in the setting, then it will be used by the get_client method.

Now that we can bootstrap an application, then we can write the tests.

.. literalinclude:: ../../../examples/unittesting/notif/tests/test_views.py
   :emphasize-lines: 16-26

Then we can write the view that implement the notification sent.

.. literalinclude:: ../../../examples/unittesting/notif/src/notif/views.py
   :emphasize-lines: 12,15

The object AppConfig is retrieved by FastAPI using its dependency injection, and the concigured get_client can be consumed directly.

Now to finalize our conftest.py, some fixture must be written to.

...
from notif.views import fastapi


@pytest.fixture
def settings():
   return {
      "service_url_fmt": "http://{service}.{version}",
      "unversioned_service_url_fmt": "http://{service}",
   }


@pytest.fixture
def configure_dependency_injection(params, settings):
   settings["transport"] = FakeTransport(params["blacksmith_responses"])
   FastConfig.configure(settings)


@pytest.fixture
def client(configure_dependency_injection):
   client = TestClient(fastapi)
   yield client

Note

To finalize, we need to start the service for real, so we create an entrypoint.py file that will configure and serve the service.

Here is an example with hypercorn. Note that the configure method is a couroutine in this example, but it was a simple method before, to simplify the example.

.. literalinclude:: ../../../examples/unittesting/notif/src/notif/entrypoint.py

The full example can be found in the examples directory on github:

https://github.com/mardiros/blacksmith/tree/main/examples/unittesting/notif

Using whitesmith

The :term:`whitesmith` package generate pytest fixture and handlers with fake implementations, its at an early stage but can be a great way to create api fixtures.

Usage:

# install the deps ( use `pip install whitesmith` if you use pip)
poetry add --group dev whitesmith
poetry run whitesmith generate -m my_package.resources --out-dir tests/

This command generates a folder tests/whitesmith with a conftest.py and a tests/whitesmith/handlers containing fake api routes implemented but that should be overriden for your needs.

Example:

poetry run whitesmith generate -m tests
Generating mocks from blacksmith registry...
Processing client notif...
Writing tests/whitesmith/handlers/notif.py

Check it out !