pytest-flask

The client provided by pytest-flask makes it easy to access JSON data in responses via the .json attribute.

Note: If your application uses a custom response class that already defines a .json attribute or method, pytest-flask will not overwrite it. You can implement custom deserialization by subclassing flask.Response and setting it as app.response_class in your fixture.

@api.route('/ping')
def ping():
    return jsonify(ping='pong')

def test_api_ping(client):
    res = client.get(url_for('api.ping'))
    assert res.json == {'ping': 'pong'}

To integrate pytest-flask with a Flask application using the application factory pattern, define an app fixture in your conftest.py file. This fixture should return an instance of your Flask application.

Assuming you have an application factory in myapp.py:

from flask import Flask

def create_app():
    app = Flask(__name__)

    @app.route('/hello')
    def hello():
        return 'Hello, World!'

    return app

Define the fixture in conftest.py as follows:

import pytest
from myapp import create_app

@pytest.fixture
def app():
    app = create_app()
    return app

Once the fixture is defined, you can run your tests using the standard pytest command.

import pytest
from myapp import create_app

@pytest.fixture
def app():
    app = create_app()
    return app

# Run tests with:
# $ pytest

Install the pytest-flask plugin using pip to enable testing utilities for Flask applications within your pytest suite.

pip install pytest-flask

To identify code sections not covered by the test suite, run pytest using coverage. This process involves running the tests with multiprocessing concurrency, combining the results, and generating an HTML report.

After running the commands, open htmlcov/index.html in your browser to view the report.

$ coverage run --concurrency=multiprocessing -m pytest
$ coverage combine
$ coverage html

To use pytest-flask, you must define an app fixture in your conftest.py file. This fixture should return your Flask application instance.

from myapp import create_app

@pytest.fixture
def app():
    app = create_app()
    return app

To use pytest-flask features, define an app fixture in your conftest.py file. This fixture should return an instance of your Flask application. Once defined, the app fixture becomes available to all tests in your suite.

from myapp import create_app
import pytest

@pytest.fixture
def app():
    app = create_app()
    return app

To test how your API handles different media types (Content Negotiation), use the accept_* fixtures as headers in your client requests. This allows you to verify that your application returns the correct mimetype based on the Accept header.

Available fixtures:

• accept_any: Sends */* header.
• accept_json: Sends application/json header.
• accept_jsonp: Sends application/json-p header.

def test_api_endpoint(accept_json, client):
    res = client.get(url_for('api.endpoint'), headers=accept_json)
    assert res.mimetype == 'application/json'

To prepare your local environment for contributing to pytest-flask, follow these steps:

1. Fork and Clone: Fork the repository on GitHub, then clone the main repository (not your fork) to your local machine.
2. Add Remote: Add your fork as a remote named fork to allow pushing your changes.
3. Install Dependencies: Use tox to create a virtual environment and install pytest-flask in editable mode with development dependencies.
4. Install Hooks: Install pre-commit hooks to ensure code quality.

$ git clone https://github.com/pytest-dev/pytest-flask
$ cd pytest-flask
$ git remote add fork https://github.com/{username}/pytest-flask
$ tox -e dev
$ source venv/bin/activate
$ pre-commit install