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Test HTTP and API interactions with vcrpy

Background

We have a simple PeopleRepository class which we are going to use to interact with the Star Wars API. The repository class implements two methods:

Method Purpose
all() Return a list of all people from Star Wars
find(**filter) Return a list of all people from Star Wars who match the given filter.

Interaction with the API is through Python's request package.

We want to write tests to test our repository class.

Solution

We are using the pytest-recording plugin for pytest which uses pyvcr to record HTTP interaction.

To install pytest-recording you can use pip:

pip install pytest-recording

Here is an example what our tests would look like:

# File: test_peoplerepository.py

import pytest
from swapi import repository

# Apply these marks to all test cases from the module.
# Instruct VCR that default cassete should be stored in "swapi.yaml" rather than
# <test-case>.yaml
pytestmark = [pytest.mark.default_cassette("swapi.yaml"), ]

@pytest.fixture(scope="session")
def vcr_config():
    return {
        "filter_headers": ["authorization"],
        "ignore_localhost": True,
        # Instruct VCR that we want to record the interaction only once.
        "record_mode": "once",
    }

@pytest.fixture
def people_repo():
    return repository.PeopleRepository()

@pytest.mark.vcr()
def test_people_repo_all_returns_expected_number_of_people(people_repo):
    people = people_repo.all()
    assert len(list(people)) == 82

@pytest.mark.vcr()
def test_people_repo_find_returns_expectd_person(people_repo):
    results = list(people_repo.find(hair_color='blond', mass=None))
    assert len(results) == 1
    assert results.pop().name == 'Finis Valorum'

Running the tests with pytest:

$ pytest tests/test_peoplerepository.py -vv --cov repository.py

Produces similar output:

============================================== test session starts ===============================================
platform win32 -- Python 3.9.6, pytest-6.2.5, py-1.11.0, pluggy-1.0.0 -- c:\sandbox\repos\pyvcr-examples\.venv\scripts\python.exe
cachedir: .pytest_cache
rootdir: C:\Sandbox\repos\pyvcr-examples
plugins: cov-3.0.0, recording-0.12.0
collected 2 items

star-wars-api/tests/test_repository.py::test_people_repo_all_returns_expected_number_of_people PASSED [ 50%]
star-wars-api/tests/test_repository.py::test_people_repo_find_returns_expectd_person PASSED           [100%]

----------- coverage: platform win32, python 3.9.6-final-0 -----------
Name                  Stmts   Miss  Cover
-----------------------------------------
swapi\repository.py      41      6    85%
-----------------------------------------
TOTAL                    41      6    85%

=============================================== 2 passed in 0.28s ================================================

Complete example

You can find the complete example in Github: https://github.com/ivangeorgiev/pyvcr-examples/tree/main/star-wars-api

Further Reading