Why?

While tests aren't required to publish a custom component for Home Assistant, they will generally make development easier because good tests will expose when changes you want to make to the component logic will break expected functionality. Home Assistant uses pytest for its tests, and the tests that have been included are modeled after tests that are written for core Home Assistant integrations. These tests pass with 100% coverage (unless something has changed ;) ) and have comments to help you understand the purpose of different parts of the test.

Getting Started

To begin, it is recommended to create a virtual environment to install dependencies:

python3 -m venv venv
source venv/bin/activate

You can then install the dependencies that will allow you to run tests: pip3 install -r requirements_test.txt.

This will install homeassistant, pytest, and pytest-homeassistant-custom-component, a plugin which allows you to leverage helpers that are available in Home Assistant for core integration tests.

Useful commands

Command	Description
pytest tests/	This will run all tests in tests/ and tell you how many passed/failed
pytest --durations=10 --cov-report term-missing --cov=custom_components.integration_blueprint tests	This tells pytest that your target module to test is custom_components.integration_blueprint so that it can give you a code coverage summary, including % of code that was executed and the line numbers of missed executions.
pytest tests/test_init.py -k test_setup_unload_and_reload_entry	Runs the test_setup_unload_and_reload_entry test function located in tests/test_init.py