Contract Testing

We currently have situation where there is a gap (in time) between when changes are made to Backend APIs (provider), and when clients (consumer) ingest or implement these changes. These could lead to breaking changes being released to stage or production or significant time passing before the consumers realize that they need to make changes.

These are the key reasons for implementing contract testing which aims is to fill the gap between changes made to the specific provider, and what the consumer expects. With contract testing in place, we would be in a better position to know when the implementations of the provider and consumer become incompatible, and when this happens. This way the provider and consumer are more in-sync with the evolution of the API.

This repo contains contract tests for TextNow APIs. Please follow the guidelines below for local development

Pre-requisites

• Tools used for this project include Python 3.11, Docker to run a local Pact broker, and Pipenv for dependency management
• Install a minimum version of python3.11 which can be found here. NOTE - DO NOT install python3.11 using Homebrew as this causes issues.
• Install Docker and Docker compose (used to run local instance of Pact broker)
• Once python has been installed locally, install pipenv and pytest globally

$ pip3 install pipenv pytest

• Install other dependencies for the project using pipenv to a virtual environment

$ pipenv shell  // activates a virtual environment
$ pipenv install  // installs dependency libraries

Adding Contract Tests

When adding contract tests, it's important to note that we are testing only the interaction between the consumer (client), and the provider of the API. We use a Pact Broker to manage the contract (or pacts) between the consumer and the provider. There will be cases where the provider has to have a certain state e.g. existing user, which is achieved by managing "provider states". To manage provider states, we use a stand-alone flask app - /src/state_app.py to manage this.

We use the pact-python library to write contract tests. The pact tests are from the consumer driven point of view and grouped into logical areas e.g. UserConsumer class, handles all interactions with the API /api2.0/users/, the EmailConsumer class handles all interactions with the API /api2.0/email/

Pre-Commit hooks

• Pre-commit hooks are used to ensure proper linting and unified file formatting for this project
• Initialize the pre-commits hooks

$ pre-commit install  // this needs to be run only once

• To run pre-commit hooks on all files in repo

$ pre-commit run --all-files

Pact Versioning

• Each pact for a consumer has to have a unique version number. If there are modifications or any more tests added, the version number will need to be updated before the pact test is run otherwise this could result in a race condition

Running Tests (local development)

• Start the pact broker container using the docker-compose file
• Note that an environment variables file default.env located in the same place as the docker-compose.yml file is required as this where the environment variables FLASK_SERVER_PORT, and TN_ADMIN_SECRET are set. Ensure the contents of default.env have the following remaining environment variables

FLASK_SERVER_PORT=5001
TN_ADMIN_SECRET=*******
PACT_BROKER_ALLOW_PUBLIC_READ=true"
PACT_BROKER_BASIC_AUTH_USERNAME=pactbroker
PACT_BROKER_BASIC_AUTH_PASSWORD=pactbroker
PACT_BROKER_DATABASE_URL="postgres://postgres:root@pact-postgres/postgres"
POSTGRES_USER=postgres
POSTGRES_PASSWORD=root
POSTGRES_DB=postgres

• Start the containers using the command below

$ docker-compose up -d

• Run tests from the terminal using pytest with the --broker-url argument
• Note: The first time you run the pact tests after starting the pact broker, the provider tests will fail as the pacts have not been registered initially. You would need to run the command below again. Another work around is to run the individual consumer tests to register the pacts with the broker.

$ pytest -v tests --broker-url=http://<pact_broker_username>:<pact_broker_password@localhost:9292

• Run individual pact tests from the terminal using

$ pytest -v tests/<test_name> --broker-url=http://<pact_broker_username>:<pact_broker_password@localhost:9292