Getting Started with HTTPX, Part 4: pytest-asyncio and pytest_httpx (Asynchronous Version)

In Part 2, we explored how to write tests and mocks using pytest and pytest_httpx for the synchronous version of the client, which was built in Part 1.

Now that we have the asynchronous version from Part 3, let's write asynchronous tests.

Install latest pytest, pytest-asyncio, and pytest_httpx

In order to test asynchronous functions, we first need a suitable asyncio pytest plugin. Let's add pytest-asyncio as a development dependency, and also make sure pytest and pytest_httpx are installed:

poetry add -D pytest@latest pytest_httpx pytest-asyncio

If you already upgraded pytest and installed pytest_httpx, then just poetry add -D pytest-asyncio will do.

Add an asynchronous test

Let's revise our test module, keeping the synchronous bits, and adding an asynchronous test:

import pytest

import pypedia.asynchronous
import pypedia.synchronous

ARTICLES = {
    "pages": [
        {
            "id": 23862,
            "key": "Python_(programming_language)",
            "title": "Python (programming language)",
            "excerpt": "Python is an interpreted, high-level, general-purpose programming language.",
            "description": "An interpreted, high-level, general-purpose programming language.",
        },
        {
            "id": 226402,
            "key": "Guido_van_Rossum",
            "title": "Guido van Rossum",
            "excerpt": "Guido van Rossum; the creator of the Python programming language",
            "description": "Dutch programmer and creator of Python",
        },
    ]
}
SEARCH = "incategory:Python_(programming_language)"
URL = "https://en.wikipedia.org/w/rest.php/v1/search/page?q=incategory%3APython_%28programming_language%29&limit=100"


def test_mock_sync_search(httpx_mock):
    httpx_mock.add_response(url=URL, json=ARTICLES)
    response = pypedia.synchronous.search(SEARCH)
    assert response.status_code == 200
    assert "Guido" in response.text


@pytest.mark.asyncio
async def test_mock_async_search(httpx_mock):
    httpx_mock.add_response(url=URL, json=ARTICLES)
    response = await pypedia.asynchronous.search(SEARCH)
    assert response.status_code == 200
    assert "Guido" in response.text

There is not a whole lot of difference between the synchronous and the asynchronous versions of the tests, thanks to pytest_httpx.

• We need to import pytest so that the @pytest.mark.asyncio decorator can be used.
• Use the @pytest.mark.asyncio decorator on the async test function.
• The tests need to be awaitable. In other words, use the async keyword before the function definition.
• Use the await keyword before calling the asynchronous function(s) we built.

Run the tests

Do the tests succeed?

poetry run pytest

Asynchronous bliss.

I hope this introductory exploration of HTTPX is useful for you as a launchpad for more robust API client projects. Happy developing.