GivenPy

GivenPy is a super simple yet highly extensible micro testing library to enable easier behavior driven development in Python.

It doesn't require any fancy dependencies and can work with any test execution framework like unittest or pytest.

It is basically a syntax sugar that allows you to write tests in a more readable way. It also helps you to encourage the re-use of setup code (given steps).

Example

import unittest
from typing import Dict

from hamcrest import *
from starlette.testclient import TestClient

from tests.givenpy import given, when, then
from tests.steps import prepare_api_server, create_test_client, prepare_injector


class TestExample(unittest.TestCase):
    def test_health_works(self):
        with given([
            prepare_injector(),  # custom code to prepare the test environment
            prepare_api_server(),
            create_test_client(),
        ]) as context:
            client: TestClient = context.client

            with when():
                response: Dict = client.get('/api/v1/health').json()

            with then():
                assert_that(response, instance_of(dict))
                assert_that(response['status'], is_(equal_to('OK')))

or simpler

import unittest
from typing import Dict

from hamcrest import *
from starlette.testclient import TestClient

from tests.givenpy import given, when, then
from tests.steps import prepare_api_server, create_test_client, prepare_injector


def test_health_works():
    with given([
        prepare_injector(),  # custom code to prepare the test environment
        prepare_api_server(),
        create_test_client(),
    ]) as context:
        client: TestClient = context.client

        with when():
            response: Dict = client.get('/api/v1/health').json()

        with then():
            assert_that(response, instance_of(dict))
            assert_that(response['status'], is_(equal_to('OK')))

Installation

pip install givenpy PyHamcrest

Documentation

def magic_function(x, external_number):
    return x + 1 + external_number


def there_is_external_number():
    context.external_number = 1


def test_magic_function():
    with given([
        there_is_external_number,
    ]) as context:
        with when("I call the magic function"):
            result = magic_function(1, context.external_number)

        with then():
            assert_that(result, is_(equal_to(3)))

But I recommend using more flexible higher functiosn that can become configurable:

def magic_function(x, external_number):
    return x + 1 + external_number


def there_is_external_number(number):
    def step(context):
        context.external_number = number

    return step


def test_magic_function():
    with given([
        there_is_external_number(5),
    ]) as context:
        with when("I call the magic function"):
            result = magic_function(1, context.external_number)

        with then("it should return 7"):
            assert_that(result, is_(equal_to(7)))

More examples

This example is from one of the bigger projects where we use givenpy to test our API endpoints.

import logging

import ulid
from hamcrest import *
from starlette.testclient import TestClient

from app.organizations.repository import TeamRepository
from app.organizations.team.core import Team
from tests.givenpy import given, when, then
from tests.integration.organization.test_feedback_submission import person_is_present
from tests.integration.steps_auth import auth_is_ready
from tests.integration.steps_database import database_repo_is_ready, database_is_clean
from tests.integration.steps_issues import there_is_organization
from tests.steps import prepare_api_server, create_test_client, prepare_injector

logging.basicConfig(level=logging.DEBUG)


def test_team_creation_for_the_organization_should_work():
    with given([
        prepare_injector(),
        database_repo_is_ready(),
        database_is_clean(),
        prepare_api_server(),
        there_is_organization(),
        create_test_client(),
        auth_is_ready(),
    ]) as context:
        client: TestClient = context.client
        organization_id: ulid.ULID = context.organization_id

        with when():
            payload = {
                "command_name": "CreateTeamCommand",
                "entity_type": "team",
                "payload": {
                    "name": "Test Team",
                    "organization_id": str(organization_id),
                    "members": [
                    ]
                }
            }

            response = client.post(
                f'/api/v1/organizations/{organization_id}/teams',
                headers=context.add_token(),
                json=payload
            )

        with then():
            assert_that(response.status_code, equal_to(200))

            team_repo: TeamRepository = context.injector.get(TeamRepository)
            team = team_repo.find_one(response.json()['id'])

            assert_that(team.name, equal_to("Test Team"))
            assert_that(team.organization_id, equal_to(organization_id))


def there_is_team(name="Test Team"):
    def step(context):
        team_repo: TeamRepository = context.injector.get(TeamRepository)
        team = team_repo.save(
            Team(
                name=name,
                organization_id=context.organization_id,
                id=ulid.new(),
            )
        )
        context.team_id = team.id

    return step


def test_i_should_be_able_to_add_the_person_to_a_team():
    with given([
        prepare_injector(),
        database_repo_is_ready(),
        database_is_clean(),
        prepare_api_server(),
        there_is_organization(),
        create_test_client(),
        person_is_present(),
        there_is_team("Test Team 1"),
        auth_is_ready(),
    ]) as context:
        client: TestClient = context.client
        organization_id: ulid.ULID = context.organization_id
        team_repo: TeamRepository = context.injector.get(TeamRepository)

        with when():
            payload = {
                "command_name": "AddPersonToTeamCommand",
                "entity_type": "team",
                "payload": {
                    "team_id": str(context.team_id),
                    "person_id": str(context.person_id),
                }
            }

            response = client.post(
                f'/api/v1/organizations/{organization_id}/teams/{context.team_id}',
                headers=context.add_token(),
                json=payload
            )

        with then():
            team = team_repo.find_one(context.team_id)

            assert_that(response.status_code, equal_to(200))
            assert_that(team.people, has_item(context.person_id))


def test_a_list_of_teams_for_the_current_organization_should_be_retrievable():
    with given([
        prepare_injector(),
        database_repo_is_ready(),
        database_is_clean(),
        prepare_api_server(),
        there_is_organization(),
        create_test_client(),
        person_is_present(),
        there_is_team(name="Test Team 1"),
        there_is_team("Test Team 1"),
        auth_is_ready(),
    ]) as context:
        client: TestClient = context.client
        organization_id: ulid.ULID = context.organization_id

        with when():
            response = client.get(
                f'/api/v1/organizations/{organization_id}/teams',
                headers=context.add_token(),
            )

        with then():
            assert_that(response.json(), has_length(2))

Contributing

Just create a PR or something. I'll review it and merge it if it's good.